I am trying to grow with hydroponics. Growbox automated system. Having problems getting started. My first seeds germinated, got the second leaves, then they all got brown and died. I think I had a fungal or mold problem from my medium which was a type of foam. I cleaned my growbox system and materials and started over. The next seeds germinated got the second leaves and are dying. I’ve changed water, used hydrogen peroxide to prevent reinfection. My pH is between 5.6 and 6.2. Temperature runs from 74 with no lights to 82 when lights are on. Humidity is around 25 to 35. Good ventilation. Not CO2 yet. I’ve tried no nutes and mild nutes. I’m at my wits end. Strains are auto Blueberry and auto Northern Lights. Maybe it was just poor seeds. I have ordered seeds from you this time and will try again. Any suggestions? Oh, I water for 15 minutes every four hours or so. My TDS is where it should be according to my instructions that came with the growbox. Also, I threw away the foam mediums and am trying rockwool. Help appreciated. Thanks.
Pictures would really help us diagnose.
The plants are so tiny I don’t think I can get any decent pics. The plants just don’t grow. I didn’t mention my lights. I have a 480 Watt Duo-Drive LED light and am on a 18/6 cycle with veg only lights on. It’s about 30" above my plants.
Is the medium getting waterlogged. Your problem is likely damping off.
I don’t think that’s what mine look like, I did have one that came up and immmediately fell over that looked kind of like that, but most of mine started getting brown around the edge and just kept going in until they were all brown. I am going to try to send pics of what I have. Only one still has much green to it. The ones in pots are ones I tried to save my putting them in soil, bu they were too far gone I guess.
@rdloffice that last one is looking alright. Have you been ph’ing your water?
I defer to @MattyBear for more advice. It seems like you have to be more cautious of overwatering. Pictures are very helpful if you can grab a few more under normal light.
The other two look like they’re beyond hope.
Okay, hopefully the last one will survive. Should I cut back some more on watering? I water for 15 minutes every four hours. I have an auto pH system on it. It runs 5.6 to 6.2. Should be getting my seeds from you guys pretty soon and get some more going.
Do you have a drip system set to water every 4 hours? Is that correct? At this stage, you should be letting the rockwool dry out a little bit but not too much. It shouldn’t be soaking wet either. Keep it moist until your tap root makes it into the bucket and then discontinue top feeding. 
Yes, it’s on a drip system.I appreciate the help. It’s nice to have somebody to go to for advice. This is not as easy as I assumed it would be to do. Thank you.