browning leaves, burn but not on tips, ph problem? deficiency?

Hello these ladies are a couple weeks away from being done and I have a problem developing here I think its probably PH related but I would love your input if you have seen this before or have an idea whats going on here please help! Thanks!

I guess I will flush like 3 gallons thru each one with PH down as I believe its too high, and some herculean harvest and hope for the best

I would guess toxic salt build up from too much synthetic nutes, but obviously only a guess because you haven't shared ANY information about your grow. It is a little hard to imagine getting a severe PH problem this late in the game unless you changed something up big time. Probably a good idea to flush.