The Last Sativa I did was Blue Dream. It always would put it's weight on last 2 weaks. For me, that was 12 and 13 weak. I would total 28-64 G per girl.
I had the same problem. I am growing grapefruit diesel and my best 2 plants started leaking sap. i'm 6 weeks in to flowering and have checked plant for bugs - none found. If it makes you feel better haven't seen it happen again. Only thing that i can corelate, was I did have a heat spike 1 day...