Without knowing more about your grow my first guess is high heat and not enough water. What are your temps like and how do you determine when to water? I don't know anything about that fertilizer but in general slow release nutes aren't great for cannabis. The one that's still green can probably be saved but the other one looks fried.

Yes those temps are probably causing your problems. In hot environments like that even if the medium is moist the plant is losing water through the leaves faster than the roots can draw it up. I grow in a greenhouse and have found that good air flow is critical. I usually leave all windows and doors wide open with several large oscillating fans running 24/7. When temps get into the 90s you will have to water more often, maybe once a day or even multiple times of day depending on temps, pot size, air flow etc. Good Luck