Why are some of the leaf tips curling upwards ? Th...

This isn't a heat, humidity, or light issue. From the looks of the slight browning and curling on the same leaf, I think you're overwatering and now you have a small root problem. Your diary environments are on key so it's easy to eliminate that issue and go to the roots. Check the last time you flushed and if so flush her. Also maybe back off slightly on the amount of nutes AND water you're giving her. Give her a good moist and dry cycle and gradually increase as she dries out. Hopefully this information will be useful!😁

Hi @ValhallasGarden! To me it looks like a combination of nutrient-burn + heat-stress. Your feeding schedule looks very strong, I hope you give them a break with plain pH'd water sometimes, or your rootmass must be very hot. And your pH is not acidic enough for soilless medium, try to stick within the 5.5~5.8 pH range or your plant's roots won't be able to handle nutrient uptakes. Plus I don't see any fans in your grow room but maybe you already have some, I've seen my plants doing this when the airflow was not good enough, adding a small continuous breeze helped a lot. To summup: 1/ double check your pH and stick to the soilless range, 2/ raise your light a bit and add a continuous breeze with a small fan, 3/ flush with plain pH'd water buffered at 5.5 and see how it goes after a few days. Hope this will help, let us know how this goes, and happy growing! 👊

Your nutes strength is ok, low even, judging by the foliage color. My bet is heat stress, raise the lights.

I would have to say this is signs of overfeeding/nutrient burn. Eventually those tips will turn yellow then brown and progress up leaves from there then die if not fixed immediately. I would do a flush with pH water to remove any salt build up. Then next feeding cut back on the additives you are using. You are a bit high with these. I would go with 1/2 of what your using on the additives. Not all strains will feed the same is probably why you haven't ran into this situation before.