Hi,
Yeah you can start feeding already but start At a low percentage(75%) of nutrients so the plant doesn't get burn( to small for a normal dosage of nutrients)and increase the amount of nutrients slowly as the plant grows and is more establish to its environment.
Happy grow!!!!!
Yes, with hydro there is no nutrients in the water at all. Only water, so you have to begin to feed nutrients at the very start.
Follow manufacturer recommendation at 25% and slowly increase throughout the grow so you don't burn your plants out.