Hydro grow, ended up with root rot

From a fellow grower:

i am growing in hydo and i end up with root rot i have 2 air stone in a 4by4 how mush time should i feed them in 24 hours my lights are good hps in veg and mh in flowering they are 400wat i have cut back from 3 hours a day to halve hour on and off in 24 hours thank you for your time

Answer these simple questions the best you can.
If you do not know, or do not use something; Just say so = NA

Strain; Type, Bag seed, or NA

Soil in pots, Hydroponic, or Coco?

System type?

PH of runoff or solution in reservoir?

What is strength of nutrient mix? EC, or TDS

Indoor or Outdoor

Light system, size?

Temps; Day, Night

Humidity; Day, Night

Ventilation system; Yes, No, Size

AC, Humidifier, De-humidifier,

Co2; Yes, No

Add anything else you feel would help us give you a most informed answer. Feel free to elaborate, but short, to the point questions and facts will help us help you smile
Most importantly what kind of hydro system are you using ebb&flow DWC?