Nute lockout ? Ph fluctuations ?

I am 5 weeks deep in flowering and admittedly I ran out of my usual R.O water and used tap water. (Which where I'm from is 5ish). I also let the soil dry a bit more than usual the last week and switched nutes. But only feed twice but with my R.O water ph'd @ 6.5 - I'm also thinking possible root rot ?

Everything I've read suggests Nute lockout & Ph fluctuations. I also read how to remedy a solution.

Can you agree this is my problem via pictures & info ?

Any and all help is greatly appreciated

those small dots look like mite damage, the leaf tips are ever so slightly burnt. You said you’re using RO are you supplementing Ca n Mg