I've never heard of anyone in rdwc running their airstones or waterpump on a timer. I'd actually say not running your stones 24/7 could cause issues, perhaps the ones your having. The splashing bubbles are what keeps your water and rockwool oxygenated imo.
I now can officially say I can place a tap rooted seedling into a completely submerged rockwool, with airstones running full blast making bubbles pop on top of my pebbles. The white spots is from that, it's salts that have dried on top of my pebbles. The only way they can get there is due to water making it to the top of my pebbles and drying lol. I actually made a video of how I so it. Now I'm Fallponics which is top feed, so this might be a huge factor in why I can and others cannot. I feel my water surface level, where the rockwool is, where the bulk of roots are, well I feel that water has a very high o2 level, when compared to most hydro systems. So I'm Fallponics with airstones... Heavy surface turning.
I put my pics in to show ya it works. I havnt really tried diagnosing your issues yet. I'd need more info honestly.
Gimme a bit to study your system and ponder.
So the first pics was when I had the rockwool at 1/3rd submerged,and it worked perfect, so two months later I tried it fully submerged and it works perfect to. I havnt top fed on my last two grows and they have been the best in terms of growth rates.
Mine are droopy because lights are about to go out in an hour.
