IF YOU CAN HELP MY 15 little PLANTS..............I'M A GIRL AT A LOSS HERE!!!!!!
I have a couple SIMPLE questions. Can't find the answers ANYWHERE, pretty much everywhere I've looked. Check out the link below... I have 15 plants under a hydro setup, drip system. The "Drip System" is NOT dripping, but actually flowing out like a faucet out the black tubes...so the pump pumps the water directly back into the plants...cycling the water continuously through when I have it turned on. The rockwools are 6 inchers, and seem to be EXTREMELY soaked....not drying out. They are encircled w/ clay pellets, and the drainage below is great.
MY QUESTIONs:
1. What is the best way to water a 6 inch rockwool cube?
2. HOW MUCH water does it need at ONE watering (ie, an ounce, cup or gallon for each plant?)
3. How much time in between should I wait, and how do I know if it is dry enough to water again?
4. How can I get the water to spread throughout the entire top part of the cube, instead of just flowing down near the stem, and directly draining out the bottom 1/2 of the cube?
5. Is yellowing between veins, from the bottom of the plant to the top leaves, a sign of over-watering or just under nuting?
I AM SO GRATEFUL TO ANYONE WHO HELPS OUT!!!!!!!!!! you guys rock 
Rock wool can hold a large amount of water for a long time. Your six inch cubes probably only need 1/2-3/4 cup of water per day at the most to keep the RW moist enough. If the roots are not dangling into nutrient solution then you have the problem of only having enough water to keep the RW moist , but not enough to keep the root zone properly fed. If you are growing plants that do not have roots into nute solution then you have to feed them more often. You might look into hydroton pebbles instead of RW if you have no other choice but to frequently water.
1) with a drip emitter or by hand, your sounds like it is missing the drip emitters and has just the tube ends letting water just flow out. Drip emitters will cut your flow into a much smaller amount.
2) Enough to keep it moist only, not wet or saturated.
3) 1-2 times per day for 5-10 minutes each time
4) RW is very porous and soaks up water kind of like a sponge does, if your watering by the stem that is the ideal spot as you want to get to the roots. The top half is getting soaked just as much as the bottom half is.
5) Yellowing can be caused by over watering, especially when accompanied by edges turning black, or black spots appearing, most other yellowing is nitrogen deficiency which can also be caused by over watering.
Interveinal yellowing starting with the older leaves first(The bottom)sounds like High ph causing magnesium deficiency, if the PH is in the range of 5.4-6.0 then its probably just deficient and can be cured with a couple teaspoons of Epsom salts in the nute solution. You can get Epsom salt at just about any grocery store by the hygiene aisle.
