Watering

How much (ml) should i be watering my one month old plants.
Specs:
they are in 5 gallon buckets.
they are one to one and a half months in.
they are under a 1000 and a 600 watt light indoor obviously.
i have a total of 20 plants.
they are afghooie.

thanks guys..

It will depend on a lot of things such as heat, humidity, and strain but I would guess somewhere around 2-4 gallons per week.