White Widow Autos (first-time grower)

By far my worst week, and I'm not sure if #1 & #2 will survive. I am assuming PH is too high (7.5 but I don't trust my tester), but PH Down may not come in time, and who knows what the issues really are. There is also a moldy pool smell, and I'm not sure which plant(s) are affected. Root rot? Impacted soil? This grow is also taking a lot longer than I expected. It may be 15-16 weeks at this point, and I was hoping for 12. Maybe I should have bought photos. Plant 1: Middle leaves yellowing rapidly. Pistils browning. Phosphorus deficiency? Plant 2: Lower leaves turning rust color and falling off. Stem leaning near top. Sulfur deficiency? Plant 3: Stems turning purple. Phosphorus deficiency? Plant 4: Stating to show rusting leaves like Plant 2. This one has been very disappointing after looking like the frontrunner.