Seeing yellow or brown tips on my Gorilla Cookies Autoflower as well. I had the LEDs on 24/7 until finding this, after doing some reading I find it could be a couple thinks, to much light, or nutes burn. I cut the lights back to 18/6 but only made sure I was not over measuring my nutes. I’m just going to leave them alone now, only a few week left to grow. Hope you find you problem, good luck.