Tropic ozz stressed out a bit due to adding a heater at the beginning of week 4. Was playing around with it with a timer amd ended up heating the plants too much for 24 hrs.
Changed the heater from timer activated to thermostat and waited a bit to see if they get better.
It's mild nutrient burn. You've got your plants pushed pretty hard with nutrients. It's ok if it stays like that but if it progresses down the leaf tip and curls upward that's more substantial nutrient burn.
probably a slight imbalance in either your feed or your ph :) I would double check everything and keep eye on her she might need but more feed or bit less if your following a feed table this should not really happen ? are you using anything new or ? nice looking bud though:) congrats