well if his temps are gettin to the 30s its possible an it doesnt say how much he waters to begin with, if he waters only a lil amount then itl dry out quicker. its possible in my experience for it to dry out that quick especially if theres no run off from the waterings hes given.
anyways it takes a lot to overwater a plant the soil needs to be quit soggy an for a number of day. he says he lets it dry out fully, wot more do u want him to say, those pics dont look like the soil is overwatered but without actually physically seeing the plants in their pots no one but him will actually be able to tell us for sure.
i didnt say i thought they were drying out, i meant to say its more likely than overwatering. but probalby isnt the problem either, il jus wait for his input on wot he grows in as its not his soil mix,pots,nutes,or water imo, ive only seen this happen with dodgy soil or those gassy tents or ph causing lockout but thats unusual in biobizz allmix soil, in theory he shouldnt even need to take ph readings.
I have watered just one time since repot and gave about 0,75lt for pot and there was no runoff. Than gave a VERY light watering about 3 days later, with fixed ph, becouse i thought that could be the problem. At that time the soil was already pretty dry, surely the first 3cm were. Then nothing till now. What also made me thought about something else from overwaterin was that the first 2 days right after watering when the soil should have been soaked plants were growing fast and well and stopped when pots began to dry.
ABout the tent: i bought it at a growshop, it costs around 150euros and it should be something designed to grow plants. So i really hope that's not the problem!