It was due to go off. I've been on an 18/6 schedule, but selfishly had the lights to go off when we go to bed, but having struggled with temps, it makes sense for them to go off in the middle of the day when it's hottest outside. So I need to change it by about 12 hours... should I leave them on for 36 hours to get the right time to turn off again? Temp is currently 26.4°C and humidity is 42%. Happy with that
Yes that will certainly help having the lights off during the hottest parts of the day. If you need to change the time your lights are on/off, always go for the longer period of light on because if the lights on time goes below about 14 hours it would induce flowering. When the lights come back on next, leave the light on for the normal 18 hours and then anytime after that you can set it for when you want the lights to go off next and then back on 6 hours later.
Pretty low humidity but nothing major, it is likely associated with the higher temperature. 26 is not a bad temp but generally don't want to get to much higher than that. Some plants can take the high heat and some can't, all strain dependent really. You are well on your way now, keep up the good work!