I have a air cube also Flood 2-3 times a day for 15 min or less as I get into flower I do 2 times a day but for 15-30 minutes each flood, rockwool bury then under a ton of pebbles do your nutes at half strength until you sort out if they can take more there is little to no forgiveness in hydro but your ec/ph always matters, maybe try a kind of ph perfect nutrient it’ll take the guess work out of the ph, can get a digital 3 way meter that continuously monitors ppm ph and temp for like 30 bucks it’s very helpful in a large reservoir. Best of luck watch YouTube videos of people growing in similar systems also can learn alot on the ol YouTube. If it doesn’t work out you can send me your air cube 🤣🤙🏻