Form the pictures it looks like the hydroton is swimming in the water.
If you got any part of that rooter in the water your gonna kill them.
You planted your cube to low.
You want to plant that cube in the top like my pic below..
U dont have to but I recommend U put the rooter in a bigger 3x3 cube and veg a week,
then transplant into the net pot like below..
You actually want that rooter to dry out once the roots hit water.
Next time put a pill bottle in the middle of net pot,
raise your water level so its a half inch below top of pill bottle.
Fill in hydroton around pill bottle till your even with top of pill bottle.
Now set your rooter on top of pill bottle and and fill in around that all the way to top of net pot or bottom of first leaves..
Water 1 time with a solo cup of water and watch for roots to come out bottom of net pot.
You shouldnt be using a very strong light or very close light untill a week after roots hit water..
Drop the water level to even with bottom of net pot 2 weeks after roots hit water.
When you flip to flower, trim the roots for long scragglers and trim just an inch off the bottom,
and drop the water line another inch.
3 weeks before harvest drop the water level another inch. the following week to 50% and 25% last week with a finishing bulb such as MH 10k
