Question for Growmie

Good job on the pots i think! Now, if you have acess to the root system check the color of the roots aswell. White is good brown is bad. See if they are growing healthy. If thats not the problem. Then really get another way to check the ph so u can can really be sure its not that too. I would like to know the temperature and Realative humidity aswell. These are just things i can think off, but i never grew with Hydro sry, cant give more especific advice, hope something helps! Really check the site i sent you throughly.. It has help me even when i was a kid 10 years ago xP

The pots are not white but black! and covered with aluminum tape!

Also, try to find your problem here: https://www.growweedeasy.com/cannabis-symptoms-pictures It has wind burn pictures, ph problems, plagues, etc...

You pointed out that your fan can be the problem. Wind can cause burns and clawing. If you have a 15-20w fan blowing directly to ur seedling i would be surprised they'd get windburn. If thats the case just adjust the fan to blow higher, ur lookign for a gentle leaf movement not shaking the leafs. This could stress the plant sand slow the growth aswell. I would really like to know if you are using transparent containers like Chevron asked... A root issue would explain aswell. We could help you more, but with soo little information on the grow is kinda hard. But this are all possibilities, you are the one who as to pin point the error. Get another way to check water ph, like liquid indicator, to be extra sure of ur readings.How old are those plants? If more than 10 days you'll have to start narrowing your list fast, or be ready to have a really hard time getting them to grow again.