Seedsman CBD 30:1 First time

Ok so im doing ok so far but ive run into an issue with heat, it has become winter here in south Africa, which means that for us its quite cold and I've had to get a heater for the room, I've got it running on a thermostat keeping it at 25c all day long, we went away for a few days and came back to see this weird thing going on with the leaves, there was new growth which I topped that looked to have nutrient burn on the new leaf growth and on the older leaves it looked like old peoples hands, all wrinkled and not looking great... any ideas on what it could be?