help pls

They look ok to me. But sometimes it's hard to tell in a pic with grow light on. Being young new growth is a greenish yellow. Are you feeding the plant yet. It is in veg stage so it maybe starting to get hungry also.

If your in coco and your not using something with cal mag in it, its likely a Mag issue. you need Mag to make best use of nitrogen so get some cal mag and u be fine. 3 week old plants dont need much at this stage but they do need trace elements to make use of the major nutes.

Those look like a solid shade of green to me. I bet if you pulled one out and looked at it under normal lighting it is darker than it appears in these photos. Tends to be the case with pictures under grow lights. Soilless is easy, especially for diagnosing problems. There is no guessing what is in the substrate when you buy it... nothing.. it has nothing! lol. So, you give the plant what it needs all the time. A well balanced mix that includes all the trace element. It is worth the effort to know the gist of what you feed in PPM - in total and per molecule. Start feeding at 650ppm (https://manicbotanix.com/calculators/ppm-in-solution-calc.php) everytime with 10-15% runoff (waste water or okay for outside garden). Observe and react. 120 N / 50 P / 180-190 K ballpark for autos is a solid start. Ca/Mg may vary due to tap water. can compare to my ppm table in virtually any of my diaries. photoperiods can generally handle a bit higher dose. if religous about 10-15% runoff or more and using a good product line of nutrients, you will maintain pH* and nutrient concentration levels. (*with any reputable nutrient lineup)