anyone can tell me what is happening to my plant, ...

Bro the temperature of your solution is too hot. The cannabis plants roots prefer cooler temps than ambient temps (around 68-71f). Your plant is showing signs of overwatering. It looks like your plants dont have a big enough root system to handle the waterings you are giving it. Try watering every other day. Plants usually have enough nutrients in the cotyledon leaves to support grow for 2-3 weeks.

My first plant did that for a little while, it yellowed and wanted to die off. But I realized I had my lights improperly placed, and I had given more stuff into the water than I should have. As soon as I read up on good distance, safe temps and good air, and not to go giving her too much juice when she was so young and didn't need it...she came back to me, stronger and better. I hope they bounce back for you....I know you aren't using fox farm, but they do have a products called Boomerang and its supposed to help with "unintentional abuse and neglect" :) these poor plants are probably pretty pissed at all of us newbies until we get it together.

At first sight, I'm thinking about over-watering issues : your soil looks very wet, I guess your pump settings is not perfect yet, you may want to increase the delay between two waterings. What's your pump settings, how often does she deliver water and for how long? Any idea about the volume given at each watering? I'll be around, good luck with this baby!