a few more photos; I'm not certain if it is clear, but many of my plants are a very bright lime green - almost yellow...

and one other consideration: the healthiest pepper plant I have is in a large that I did not fill with 5:1:1, instead using (I think) MG Potting Mix (though it may have been Dr. Earth's too). That does, of course, increase my suspicion that it is my soil mix causing (or at least contributing) to my troubles.

By the way, I don't think DE is very effective against flee beetles. It is most effective against crawling insects. Flee beetles jump. But, flee beetles are not really a problem if your plants are healthy to begin with. My guess is that your pepper plants were planted out too soon. They should be at least 8-10 weeks old, and older is better because they grow much more slowly than tomatoes. Temps should never go below 55 at night and days should be in the 70s or above during the day. Plus, peppers really resent wet soil. I am just about to plant out my peppers today. I planted my tomatoes, which are the same age as the peppers, on April 30.

My guess is too much rain....too little sunlight/heat. Peppers like it hot.

Temps are heating up now, so you should see a drastic change in them.

It looks to me as if you have White Powdery Mildew (or mold)

I recommend occasionally spraying the plant leaves with a mixture of 3/4 tablet of Aspirin to one gallon of water. Use uncoated tablets and spray about 2 or 3 times a week.

This mixture also greatly improved health and strength of plants and promotes growth in seedlings and sprouts.

@Jimmy Salen: I think you are seeing the DE dust and not powdery mildew. And the cure you recommend is not considered effective by most experienced gardeners.

Just want to say thanks to everyone. This past week has been sunny and in the 80's and low 90's and the plants (for the most part) have perked up nicely, though some of the smaller plants have some catching up to do.

I had surmised that sun would be better than my fluorescents, even on cloudy days. But I was woefully wrong, and especially so when the rain and chilly air camped out here for 3 weeks. As a result, some of the smaller seedlings have a lot more catch-up to do than the plants I moved outside once they were more established.

So one lesson for next year is larger seedling containers. I had started these in 3" jiffy pots, but peppers seem to outgrow them and become rootbound pretty quickly. So next time, I'll be using my 2 gallon pots.

(as an aside, does anyone know how containers are rated? I purchased 100 2 gallon containers thinking that they'd be about twice the size of a gallon milk jug. As it turns out, they appear to be the size of about a 1/2 gallon milk carton. What gives?)

That doesn't sound right. A 1gal nursery pot is around .75 liquid gal and a 2 gallon nursery pot is around 1.6 liquid gal.