Definitely nutrient burn from you giving too much nutrients. Don’t blame the nutrient company lol, 99% of why plants die is because of human error. It’s ok though, happens to every one at least twice haha.
Flush your soil with 3x the size of your pot. If your pot is 3 gallon pot, then you want to flush with 9 gallons of water. But you better make damn sure each one of those gallons of water is correctly pHed or it will throw off your root zone pH.
After you flush, wait a couple days. You can add nutrients back into the soil, but only do 1/3 strength, or 1/2 strength of the recommended dosage.
And you HAVE TO get your tent air temps down. 80 during the day is ok, but 80 at night is terrible for the plant. Try adding frozen water bottles to the tent. It’s the easiest cheapest way to drop temps. Do you have any fans, or intake or exhaust vents?