7.0 is neutral. marijuana thrives at between 6.5 and 7.0ph. anything out of that range and the plants will halt absorbtion of nutrients and cause lockout in some cases.
Not in hydro. 5.5-6.3 is correct pH.
5.8 being ideal.
7.0 is too high. In soil you can run the PH high like that but not in hydro you will get lockout. Lower PH is ALWAYS better than higher PH.
Temp is way too high. Best rule of thumb is 70/50. 70 degrees and 50% humidity. Bring humidity down in flowering.
Fans won't cool air they just move it around and in many cases the motors running 24/7 will just increase the ambient temperature. Small A/C unit is what you need. On Craigslist you can get a used one for $50.00.
Sounds like heat stress combined with Mag deficiency. Mag deficiency is common as you go into the first couple of weeks of flowering. The Epsom Salts will help if this is the problem. To correct the problem quicker foliar feed 1/2 tsp to 1 gallon of water as well as give them some in their feed water. Make sure you completely dissolve it.
I add Botanicare CalMag+ to every feeding at 1/2 to 1/4 strength. I cut it out after 2-3rd week of flowering. Epsom Salt is cheaper but I don't think it's as easy for the plants to absorb.
