Brown leaves on an Auto

Not sure what to make of this, kinda happened over the last couple days, nothing really changed. Is it possibly heat related, even though I'm using LED I had the RED leds kinda close to the plant the last few days. ( moved it away and flushed the plant so far.) let me know any ideas. I thought maybe Phosphorus Def but I don't wanna assume, and the PH is 6.8 right now. 6.6 before the flush.

No one's able to assist on this one?

Flush right away, you ph looks to high and lay off the nutes for a few waterings.