anywhere from a week to 4 weeks depending on the strain. Most plant specs I have seen say anywhere from 8 to 12 weeks. They will pack on more and more trics and resin as the days progress. You will have several days to pick the right time of harvest, it wont happen all at once. It takes about 4 days to a week for trichs to turn totally amber. Most choose about 10% to 20% amber as their harvest point.

Make sure your water is clean since they are hydroponic. When you stop feeding the plants you have to dump the water and put in fresh, but I'm sure you did that already.