8 week flowering OB - yellowing + rust spots. Pics

This is my orange bud plant in FFOF soil, with the Fox farm nutes trio. Started flowering on 4-20. Only watered Ph around 6.5, runoff ph is usually a few tenths lower. They are under a 400w hps. The problem started happening about 2 weeks ago, thought it was nitrogen def so gave them a little boost. They burned a bit so i only fed with water. The yellowing has only gotten worse, and now im getting rust spots. I have a feeling the ph could be off, but i dont see how because i have been careful. Anyone have any ideas? I feel like this is an easy fix but i keep changing my own mind to the point where i have no idea even after looking at all the self diagnose pics. I suck, please help.

how much longer u guna flower for? buds are looking nice still, maybe u should just flush for the next week or 2, plants yellow and die during the end of flowering so maybe ur just getting close to harvest

Yea that is true, i thought maybe they could go for another week or 2 before flush, the buds seem like they still have some filling in to do. However this plant actually has a few seeds because of a past hermi which could reduce bud production i assume. I actually have 2 clones of this plant that are a few weeks behind and having the same issue, so either way i kind of need a solution. In pic 2 you can see both plants, the younger one is to the right and seems to be getting more rust spots than the older one rather than just yellowing. So any input is great, but def going to chop the older one down soon.