HELP! What is the problem here?

[ufzsolo]

Hi y'all

I have a wee problem (see on photos). The leaves started turning yellow, and the plant is kinda drying out. Can't find the reason. PH good, PPM good... I had like 4 days when my AC didnt work and there was around 30C in the room but that's all I can think of. Any ideas?

[Rwise]

The plant in pic 2, right side looks gray/black around the trunk, that could be bud rot and may also say root issues.
Could be heat burn.