I doubted whether it could be low-N deficiency because you said :
>> "5 or 6 bags of good compost into the soil with some composted cow manure"
However, around here, "Cedar Grove" compost looks like it has a lot of wood shavings or sawdust, and I don't know how much area those 5-6 cubic feet were spread over.
IF your bark was finely ground, or had any sawdust mixed with it, and if you have a LOT of that in your soil, and they were not at all composted before being sold, MAYBE as soon as they were mixed with real soil they started taking up nitrogen. In that case, your added compost, and even your added manure MIGHT not be keeping up with the nitrogen demand from the compost or bark.
That's pretty weak speculation!
But you can diagnose it really easily by spraying a little soluble N fertilizer on the leaves. Chelle suggested organic sprays, and if you have those on hand it should suffice. But one tsp of Miracle-Gro would do the same thing and not attract animal pests. You can rinse it off the leaves a few days later if being organic is a priority. To me, testing for a nutrient deficiency is a sufficient reason to "be science-y".
>> I have an irrigation running on it every other day if it isn't raining.
>> I'm wondering if your plants' root/crown areas are just a bit too wet at the moment because of this.
If the organic soil (high bark content) was finely shredded, it probably WOULD hold too much water.
Maybe you should only irrigate them again after they have drunk more of what you gave them yesterday.
Coarser bark chips (2 mm - 1/4") would promote drainage and retain less water. So would coarse Perlite, granite grit, or crushed stone. But they would have to have been mixed with the soil to help. Top-dressing won't help, especially not with vermiculite, which holds excessive water.
I like digging, so I would be inclined to dig a trench next to the bed where one plant is yellower than the rest. A hole or trench below grade would give excess water somewhere to drain out TO, and also encourage evaporation from below grade. Those help remove water and admit air.
Also, if you irrigate and then see a puddle in the trench, you'll know that you're irrigating more often than necessary.
Also, if you have a trench that goes 3 or 4 or even 5" below grade, you can push a finger into the bed from one side, at a good depth to gauge whether you need to irrigate. If most of the root zone is 2 to 12" deep, and soil is damp or even wet 4 inches down, the plant is probably getting plenty of water, but maybe the roots wish they had more access to rapidly-diffusing air.
Imagine trying to breath if your head was buried 6" to 12" underground, and the soil had fine texture, and was watered until good and soggy every other day. Gasses diffuse very slowly through wet soil unless water has drained OUT of enough medium-sized voids, pores and channels to provide pathways for gaseous diffusion.
