Hi All - new to forum, hi everyone! I wasn't sure the best sub forum to post this question so I figured 'ask a question' wouldn't be too egregious (: please point me to the better sub forum if you think there is a better spot.

I am in the process of figuring out how to grow seedlings indoor for next season. I have LED grow lights and am using sterile seed starting mix. I am having issues with my tomato seedlings during my testing. They appear to start well but then the leaves start dying off. I've attached a few pictures (you can see the pepper seedling is doing pretty well). The tomato seedlings are Cherokee purple. I did do liquid fert but only to 1/2 The seedlings as I was testing so I don't think I over fertilized. Based on my research I think it may be over watering but I really haven't been watering that much and I felt I kept them moist but not wet. I have a fan going for airflow. Any thoughts would be great. Thank you!

Its really hard to tell what's going on with the purple sun coloring everything in a lovely purple hue. Do you have some white grow lights interspersed with the red/blue?

Can you take new photos in natural light?

Hello Bigant,
Welcome to the National Gardening Association. Since the lower leaves seem to be in trouble and the newer leaves look pretty good, I suspect a nutrition problem. Plants that have a shortage of some nutrients will "steal" those nutrients from the older growth to use for the newer growth. So lots of detail about the nutrients would be appropriate.

Incidentally, Calcium is also an essential macronutrient (plants need quite a lot of it right after the usual Nitrogen, Phosphorous, and Potassium) I use Calcium nitrate as a component of my indoor nutrients. It is available at most hydroponic grower suppliers. I supply Magnesium via Epsom Salts (Magnesium sulfate) available at most supermarkets and pharmacies. Both Magnesium and Sulfur are vital elements for plants. Plants also need several "trace" elements. Just out of curiosity, what is your water supply? (Plants don't need Fluorine.)

I know that plants need only the red and blue light, but they mix to a hideous purple. I suggest you switch to white grow lights for your own pleasure.

ZM

Please post some photos taken in natural light. There is no way to tell what is going on with your plants in this light. But if that is white stuff growing on the soil, you are overwatering.

Plants use ALL the colors of the light specturm, even some green. Plants have a life exoectncy of about 6 months without the rest of the colors, more than enough time to grow a marijuana plant but that's about it.

Unless you are a chemist, don't add nutrients willy-nilly. Find a well balanced fertilizer with micronutrients.

Don't ever use Epsom Salts. It makes plants look better but masks whatever is really wrong.

Calcium is used in very small amounts, there is usually enough in the soil and your tap water. Blossom end rod is usually caused by inconsistent watering practices, not a lack of calcium.

Seedlings don't need fertilizer until they have a couple sets of adult leaves and then should be used at a lesser than recommended dilution.

You are right that plants recycle nutrients in older leaves, sometimes sacrifiing them for new growth but, that in itself does not immediately point to a nutrition problem. The problem could also be insufficient light or overwatering.

Thank you for the welcomes and the response. Below are some better pictures without the grow lights on.

I did use fertilizer but only once they had a few real leaves. Below is a picture of it.

Welcome and Thanks for the white light pictures!

I think you're trying too hard. I've grown tomato from seed plenty, they are easy and fast growing for me. I rarely think about fertilizer. Maybe give a little at four weeks. In six weeks they are getting too big for indoors and beg to go out.

Try a few under white grow light, fresh potting mix, don't fertilize, see what you get in six weeks. Maybe get a packet of cheaper tomato seed for the learning process.

I think it's the lights you are using. The seedlings look stretched to me, as if they aren't getting enough light. As Sally suggested, use white light and lower the lights to just right above the seedlings, raising them gradually as they grow.

I was concerned about the lights but all my research suggests they absolutely can be used. Also how does that square with my pepper seedling doing well?

Again, really appreciate the responses and help.

I agree with Sally and Lynda, not enough light.

If you are using only red/blue light, your tomatoes (and pepper) are not getting enough light. Red/blue are the part of the light spectrum most used by plants just as nitrogen, potassium and phosphorus are the nutrients most used by plants. But, plants won't grow on just NPK, they need all the other nutrients in smaller amounts. Plants also need all the other colors in the light spectrum, just in smaller amounts. You can use the red/blue lights but add white light to your setup.

But even under white light, your plants (including the pepper) should be much shorter and huskier at this age. Double your lights.

Your fertilizer has way too much calcium. Too much calcium blocks potassium and magnesium from being absorbed by plants.

These are the grow lights I am using

Hytekgro LED Grow Light 45W Plant Lights Red Blue White Panel Growing Lamps for Indoor Plants Seedling Vegetable and Flower (2 Pack)

I won't let me post link because I'm a new member - sorry!

That is the sort of LED light (red/blue/white) you want but that one just isn't bright enough to do what you want it to do. You need at least 300w but 500w would be better.

Thank you for the feedback. There are so many lights out there. Do you have any suggestions?

Hello again BigAnt,

" There are so many lights out there. Do you have any suggestions? "

I recommend the book Gardening Under Lights as a good source of reasonably up-to-date information.

https://www.amazon.com/dp/1604697954/

I started my indoor gardening under lights in 2005, and things have changed a lot since then. I am still using overdriven T8 fluorescent bulbs in various blends of white light, only because I have them. My bulbs are rated for 20,000 hours, but T8 fluorescents are now considered obsolete. But I continue to use them simply because I have them and they work and it would cost considerable money to upgrade my lighting to current technology.

You have a lot of options for your light sources for gardening under lights.

ZM (not associated with any product or vendor mentioned or linked)

Hi guys,

I freely admit that my T8 fluorescent lighting is very obsolete, but it has been effective at growing large zinnias in small 3-inch square pots. Which I mercifully re-potted to 5-inch square pots. Click the pics to see them larger.

I really should have re-potted those to 8-inch square pots, but I got a good yield of hybrid seeds from them in the 5-inch pots.

ZM

Ummmm.... I don't quite know how to tell you this but, those Zinnias don't look good. I would guess its a nutrient problem but they could also use more light.

Just an update guys. Adjusted how I was watering/how much. Still used the fert. And put the lights closer. Way more success!

Wow, a hundred percent improvement! Doesn't even look like the same plant! Hats off to you, you can officially call yourself a tomatohead now!