Need help ASAP

I just realized im having a HUGE ph problem I belive. Rusty spots all over fan leaves.. fan leaves yellowing/browning dying. Colas are drying out.

I think i might be having a nute/lockout PH problem.

So to fix im going to flush all my plants again.
(Does the flush water have to be PH adjusted?)

Should I test the runoff?? Of which gallon the first gallon i pour in middle one or last one? Or does it matter?

I need to get my PH under control now!! Im week 5 flowering and I guess they have been suffering from this PH problem for a while.

flush should be phed. cal mag to early gave me "rust one time. if you fed alot my guess would be to flush but i dont know your grow do you have a digi for ph?