It's both. It's overwatered AND it's heat stressed. The leaf edges and almost "shriveling" look come from heat stress. If you're getting temps of 86 degrees and up it will slow growth, at least indoors and according to every book I've read on the subject. Outdoors is different, they seem to like the heat as long as you keep them watered, I'm not sure why it's so different indoors, but it is. The leaf tips curling under could definitely be from over watering, but it could also be lockout. You've GOT to know your PH levels, EVERY TIME you water or feed. If you add nutes, PH the water after you've added them all, then water. Also, composting teas, boogie brew and the like, are GREAT for helping you get your garden's ph levels back in balance, you'll save a grip on nutes as you'll use half and the plants just love that shit. My water here is so bad, comes out of my tap at 8.7-8.5, seriously alkaline, and if I was to just water with it, I'd be poisoning these plants. As is, I run it through a filter and into a 30 gallon res at least a day or two before watering. I let it sit out so any residual chlorine can dissipate and ALWAYS balance the ph right before I water or feed. I'll water a few plants and let the runoff from them collect into one saucer and then I'll test that as well. I usually shoot for a runoff ph of 6.1-6.3 and depending on what my last reading was, is pretty easy to buffer by raising or lowering the ph of the next feeding. It won't matter how much or how perfect you measure your nutrient content, if the PH is out of range and the plants can't take them up, and the further you are out of that ph range, the more problematic your grow will become. Blue labs makes a great pen, and I've used a couple, it's the best one I've used. Good luck with your grow!
Also, I noticed you've got a box fan next to the plant. You don't want to have the fan just blowing on the plant. I think doing so could be some of the problem with the leaf stress, something that oscillates is much better.