You are basically doing it all wrong.
The rockwool should be soaked in ph adjusted water, shake out excess water then put in seedling.
Then put the rockwool cube in a covered germination tray - DO NOT PUT ANY WATER IN THE TRAY!!
When the rockwool starts to dry out - dip just the bottom of the cube in ph adjusted water for one or two seconds.
You need no nutrients until the plants get much larger - a couple of weeks.
When the roots break thru put them in your growing environment.
......I 'd really consider following this with the rest of your seed. And a dome helps keep the RH up without drying the rw so fast. What kind of temps are your res h2o?
I 'd say, if you can salvage any of those to flush them real good with your peroxide mix(I'd use like Cannazyme or similar), let dry out a bit and get back in the tray and never put solution directly into the tray but dip the corner of the rw in your solution...... If you going to keep them in rw I would also recommend you to get some kind of covers for the tops of the cubes, or even make them out of panda film or garbage bags. Most anything exposed to light that is damp/wet is gonna grow sh*t, and your best off to just keep any of it from being able to start. Key word here is "Prevention"---hahah..
Yeah, Iam following a couple of thcb grows.... Even the real nice ones I've seen stretch. My mother comes down today as this isn't going to work for me. The buds are fair sized, just not enough to justify all the stem......imo. I cant even get a good pic of the few I have in 12/12 right now because the room is flooded with ak47, which has already proven itself for me<---I just cant get over the strong odor, and I was warned. But the thcb stretched when growing with the ak47 and I had to bend over the tops and even just said f it and cut one off. So the ak is right next to it with pop can size buds..........same system.
So what do you go to from the small rw cubes? Do you have good ventilation in there?
Great Luck to you!
But dont just 'accept' the fact that algy is growing; do whatever you have to to get rid of it. Period
growinman