You mean yellow, double check the color. It looks like its fading from green to yellow. If that is the case then double check these: Ph Nutrients (not too much or too little) More than likely it's just a little off, my plants did the exact same thing when they were this small.What's more important is that the new growth (top leaves) look fine. Just make sure to water on a good schedule and make sure you are not burning them with too much nutrients. And most importantly, be patient!