Answer: There are several possibilities, but the most common in my experience is either cool temperatures, too acid a soil, or a lack of phosphorus. If these are seedlings, you might try a bit of complete water soluble fertilizer for foliage plants that includes micronutrients and make sure the room temperature is about 65 degrees or more. If the plants are in the garden, it may simply be a matter of planting too early into cold soil. However, it would be a good idea to run some basic soil tests for nutrients and pH and find out for sure how your garden soil is. I hope this helps you troubleshoot.
Q&A Library Searching Tips