Looks like nute burn to me. I speak from experience, I just gave too many nutes to my plant (used the wrong mixture...suck) and the leaf tips look just like yours, brown on the tips.
It doesn't look like a heat issue, because that will burn the leaves all over. If you accidentally added too much nutes then you can flush the plant and that should help. (Flushing is done by watering the plant with 3 times the water you usually water with, until it runs out the bottom of the container. Don't worry, all is not lost if you flush quickly. Hope that helps.