problem with new potted Tomato plants

Hello this is from Paratrooper Robert I am an old jumper and This green house is new to me and I need some advice .
I am in Zone 7 and I have raised peppers and Tomatoes and some herbs from seed . I have some great looking Tomato plants but some are turning yellowish green on the bottom leaves . I am new to green house gardening but I have raised a garden for over 30 years and this is my first go around starting and raising my own plants from seed . My herbs are great the peppers are good and some are great . I have put about 25 tomato plants in 5 inch pots and they are all great and thick stemmed and very healthy . But I am concerned about the ones still in 3 inch pots and they are the one turning the light yellowish green on the bottom leaves . Any advice from anyone . Thanks a lot from an old paratrooper .