What is happening to my young plants?

Mg,K lockout due to Ca excess

Your coco looks incredibly dry............try watering until you get some run off and then see if they perk up.

70 rh% is alot of moisture for 72f, hard environment to breathe, hard environment to photosynthesize at low temps. Plastic pot prevents oxygen action of rootzones also.

Hi, Which substrate are you using? All Mix or Light Mix? What is your lamp setting in % and how far is the lamp hanging from the plants? Are you already using fertilizer? How much water do you give the plants? What is the pH value of the water? Unfortunately, there are many questions that need to be answered first. I think it’s light stress. Reduce the light intensity a bit and give your plant some CalMag.

It appears that maybe you’ve given them too much nutrients too soon. Your light DLI on a young seedling need only be around 15-20 for the first couple of weeks or maybe 20% power and 24-30” off the plants. Some are more sensitive than others. Your VPD plays a big part in a young plants health as well. You have several grows so this may fall into that category. Always check the PH to ensure it is correct, for the medium you’re using. If it’s not right, you’re guessing at what is wrong.