Need Help!

I am growing "Big Bud" in rockwool using the general hydroponics flora nutes
They are 4 weeks into budding
I am getting browning on the edges of the fan leaves

I am at 6.2 / 6.3 ph
The ppm is 700-800 using the aggressive bloom ratios

Any suggestions?

bump.......

ph is a little high. I use fox farm and keep my ppm at about 1500 during flower.ph (not sure of how your growing) for hydro or aero should be around 5.8-6 max