In earlier post, you stated that they’re in a plastic seed starting system or dome. What kind of growing medium did you use? Chances are they just need nutrients now that they’ve sprouted. If they’re already maintaining climate above 60 F and getting decent light, then it’s probably nutrients.
Best option is to use something like Mel’s Mix from the book Square Foot Gardening. If you don’t have the book, it’s basically a mixture of many types of organic stuff – peat, soil, mushroom, castings, seaweed, etc. If you have a good gardening store nearby, they may have a pre-mixed bag of good organic stuff.