Did they go dry for a few days? Too little water.

Could they be getting too much water? Are the new pots draining?

Might they need a bit of compost tea? Undernourished?

If the water is right, they might be in the first stages of wilt disease, often the yellowing will start on one side of the plant and then spread, which could mean the loss of the plants.

Here is a link that might be useful: HarvestToTable.com

Stephen, They certinly didn't go dry. I have them in a flat and add water to the flat. They could be getting to much water. The pots are draining fine. I used a mild solution of 1/2 the suggested amount of miricle grow plant food to the water when I transplanted them. It doesn't seem to be affect all of them just my Burpee Flavor Burst Sweet and the California Wonders and I have six other varieties that seem uneffected. Could it be over watering because I do keep it moist? Thanks Butch

Add a small/diluted amount of fertilizer.

You've probably "used up" your seed leaf nutrient power and your seed starting mix is bare of nutrients...they could also be getting too much water...or it might be aliens. Spooky.

Yellow of leaves in seedlings is almost always too much water. This is especially true for peppers that prefer to dry out between waterings.

The yellow leaves will likely fall off but if you reduce the watering - never leave them sitting in water especially - the new growth should be fine.

Dave

Try sunlight & like digdirt says, a little less water.