Having a problem with my greenhouse hanging baskets

I am new to this forum, and don't have a digital camera yet. I had a question though, and wasn't sure exactly where to post it. We planted about 1400 hanging baskets this year for our farmers market business. We planted the hanging baskets all by plugs. We started them in March in our oil and gas greenhouses, and have been having problems with "yellowing"/"bleaching" of the foliage. We fertilize with injector powered Peters. The centers of our plants are dark green, but the outer foliage are yellow. I wish I had a picture to show you. Have been growing hanging baskets for years, and have never had this problem before. Anybody have any ideas on what the culprit could be, or what I could try to remedy this. We have cut many of them back, to see if the problem is going to persist.

Have you tested the PH and the EC levels of the soil lately? Whats the crop thats doing this? Petunias? Off the top of my head I would say that your PH is off and its preventing a micronutrient to get to the plant. If you can tell me the present PH and the crop I can maybe help you better. Its definitely a nutrient deficiency of some sort and most likely tied into your PH. Have you switched your soil medium or fert this crop? Either might give you a different PH.