You're on the right track. Your pH is definitely not optimal. The root of the problem is that it got there because you continue to overfeed.
In your early veg pics, the N was like another poster said "incredible". As they continued to "eat it up" you fed more into flower... Salts began accumulating which in turn brought your ph down.. which brought on defs and a lockout or two.
At any of these points, you should've measured ph when trying to diagnose your issues, and then if it was acceptable then you would've treated the according deficiencies. But you cannot logically know what you have without a ph
Please stop assuming what a healthy plant should look like. hope your next ones fare better