Stumped, need help identifying what's wrong, thanks!

Pulled several leavfs off of my 4 week old Blue Mystic auto this morning, photo of both sides of one of the affected leaves attached, Indoor grow, 2x2 tent, active ventilation, 24 hr lighting 600W LED, switched on red lights 2 days ago. Advanced Nutes perfect PH, just switch to bloo, 1/3 strength, plus mammoth, cal.mag, silicon sup. Watering every second or third day. ave temp is 80deg, RH ~20% (have been hoping RH would increase as I increased watering). Have similar leafs on one side of plant, 8 total mostly leafs on bottom. Plant is about 9 inches and bushy. Also ground Jack H auto alongside in a separate container, same nute sched, showing none of these signs. When I watered yesterday I splashed nute mix on leaves.
Can anyone help with a diagnosis? Rest of plant looks strong. Also any recommendations for increasing RH in a small tent? Thanks

J. Straw.

A damp towel wicking from a bucket of water helps.

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If you are using Pass through intake hole at the bottom off the tent you can set a plate of water with a sponge close to the outside. Use a piece of flex to get down to the same level of plate. Also small humidifier sitting at same place if needed. Good luck

Thanks for the advice, I cut off all affected leaves, no recurrence. Humidifier is on the way!