How much water needed?

I am hand watering currently until there are more roots. How often does it need to be watered. It is in rockwool, obviously. 400w MH 15 inchs away.
My PH is currently a little high, but everything is starting to droop, and I have a couple plants that the leaves are turning yellow from tip to base, and one or two that are turning yellow from base to tip of the leave. These are just 9 days old.

Does any one know if the light is to close or has had to much water? Thank you for your help. I am new to this growing stuff.

how often are you watering? you need to let the rockwool get dry between waterings. Once a day maybe less in a humidity dome at least till the roots start leaving the rockwool more. The idea is to have the water drain out. The plants roots will follow the water out so if its not draining you're suffocating your roots. gl

btw i use a similar system but i use a soiless mix and transplant into my hydroton. Keep close eye on ppm\ph. 5.8-6.3 what i use but 5.5 is ok. plant that size maybe about 2-300ppm depends a lot on the strain.

ok, I am watering way to much. I have been watering maybe 2 or 3 times a day, and just making sure the rookwool is completely wet. How long does it take for the roots to make it out of that one inch cube. And once the roots are out can I leave the drip system running 24/7. What soil less mix do you use? I am hating this rockwool. And want to switch. Do you think I could cut the rockwool cubes in half so the roots don't have to travel so far to be out? That is if I continue to use rookwool next round. My PH is extremely high, 7.2 or so. I have PH down coming in the mail tomorrow. Which has been another reason I have been hand watering with rain water. Thanks a lot for your help. I appreciate it for sure. Since this is my first grow its kinda stressful.