Hey there i know it gets frustrating and finding solutions are important. But for right now, just calm down and get through this grow. Most plants will have yellowing leaves as the go further into flowering, especially when you remove the "grow" nutrients like you should. Your plants have also had ph fluctuations which can cause problems, the changes up and down. Try just keeping the nutes low and the ph consistent for the rest of this week. Alternate between plain water and then fed water and watch for things getting worse. Lots of damage wont recover, but if you can stay at where your at and not progress further than that's good. 👍