green crack / heavy hitters

This is my first grow. I feel the box is too hot sitting at 27/28 degrees and min is at 23-24 (when lights are off) Should i add an extra intake fan or do i need to upgrade my exhaust fan to remove heat? The leaves on the green crack turn upwards. while the heavy hitter is looking nice (to me ) can someone advise what to do here? Is this just the heat? I am using Terra Professional soil which i will change to terra coco on my next grow. Ive only done 1 shot of nutrients so far and that was a week ago. Planning to do another on Sunday for each plant. UPDATE: Hi all, thanks for commenting and the advice. Ive written a little update / summary answers to all comments below. I will upload further photos of my grow box. and yes it is a minish grow box (is a full size fridge) but here are its contents. - 1x 6" exhaust fan - 330 M3/Hr - 45dba (this fan is too loud so im going to replace, up for recomendations) - 2x80mm 240v intake fans - 52.8m3/hr EA - 35dba - 1x6" carbon filter - 2x6" clip fans (internal fans) - 2x80mm pc fans (internal fans) - 1x 300watt LED light ( 2 internal fans) 1) my humidity is actually 70% i was wrong writing 50%. does this mean the heat is the main issue for the leaves curling? the light is at 40cm so i didn't really want to lift it anymore. 2) I will start to water the plants in the morning as that is when the lights are off. i will continue watering 500ml-1l every 2-3days depending on the soil dryness on top and the weight of the container. 3) i have just used about 3.5ml of terra veg nut and 1l of water yesterday per plant. is this once a week ok or should this change? 4) any advice on altering PH ? i feel I cant get the technique right. i use ph down anyone have recomendations on how much PH down to use per 1l? my water i use is pearu pure water thanks again! is reassuring some aspects are good.