issues day 30 Flower

My plants were doing great up until about 2 weeks ago. This is a first time grow with little no guidence except the internet. 30 days into flowering, it looks 4 of my plants are yellowing and fading hard, clawing leaves and nute burnt tips. I dont think i transition fed them right from veg to flower nutes. Bud growth doesnt seem impacted, but after checking the ppms they were pretty high. 1800 - 2000 between all of them. I am using tap water with a ppm reading of 450. My solution as an immediate fix was to water them down to around 900-1000 ppm. It seems as if the extreme yellowing has slowed down or stopped, but the clawing remains. I had planned to water down again once dry to around 500 ppm with a ph'd water and mammoth p solution. And then re - introduce flowering nutes (fox farm) for one last feed before they need flushed before harvest. Any confirmation on this idea or other ideas are helpful!