What kind of lights are you using? How far are your lights from the plants?.How often are you watering them?Are you giving them anything else besides water?What kind of soil are you using?
First of all,your humidity is too low.It should be a lot higher than 27%.But it looks like your soil is very wet. You need to answer those questions and someone will help you.
Lets see i'm using sta-green potting soil the i have a cfl on them and it's about 3 inches away. I know the humidity is low but their new home is not yet livable i'm working on that today and it will be an inclosed area where the humidity will be trapped in there. o'm only feeing them water with a spray bottle.... and the yellow one looks a little better today.
it'll be fine,almost all of mine do it.It's due to the low humidity,and they'll grow out of it.Let the soil dry up some to give the plant all of the micro nutes that are in the soil,it helps.