How much to water how often?

I got a new set of clones today and I might be overthinking it but I'm trying to figure out how much i should water them.

the clones are rooted in 3 in rockwool cubes
the cubes are in 6 in net pots with about 1 inch of Hyrdoton balls under and surrounding the cube.
the net pots are in a topfeed/nft system
they are currently under T8 fluorescents now. I have 3k MH but i think it may be overkill?
temp is 75f
humidity is about 45%
I'm feeding them calmag, weak maxibloom, and superthrive
feeding now every 2 hours for 15 mins

how much should i be feeding them?
any potential problems with the placement of the dripper? "check picture"

Each to their own but I stay away form larger rockwool, they retain too much fluid and keep your roots saturated when ya plants are young and can stunt early growth (poor oxygen to roots). I also don't like top feeders for many reasons. Once your roots bust the rockwool and reach the flowing water underneath, get rid of those top feeders and leave your NFT running full time when lights on, everything off during lights out.

I agree except for leaving it running all the time. That just unnessessarily adds lots of heat and wastes electricity. I run mine 80sec on and 8 min off.

We have found many problems with troughlike constant flow grow systems. It is not advisable to use superthrive in hydro. I always go 1/6 per gallon on the ferts as recommended for dirt.

I have the perfect answer. when they are thirsty. place your finger into the soil. if your in a five gallon pot . should be at least 2 inches deep dry before you water. how often depends how big what stage that plant is in. and how dry hot the lighting you use. size pots . soil. I water veg every 4 or 5 days. and flower every day. then late flower every 2 days.

sory thought you were in soil stupid me.

the system only has a top feed. I said NFT because the nutrient does travel down the tube returning to the rez creating a NFT for the plants closer to the rez. Only plants that do not receive this NFT is the ones farthest from the rez.
i have a cheap timer from home depot that does 15 min intervals.
im worried about the dripper placement over saturating the rockwool with the waterings being every 2 hours for 15 mins.
and I'm also worried the roots under the rockwool in the hydroton may not get enough water.
I guess ill run to the hydro store and pick up an ART-DNE timer?

buy a pump and a bit of tube.... tah dahhh NFT.