A close picture would help tremendously, like i think i can see turgidity on the 2 plants that are probably worrying you the most but i'm not sure.
To me, they suffered from hydric stress in week 6. Your humidity is indeed too low but to protect itself the plant will kinda roll its leaves, which i did not see at all in any picture.
If it wasn't hydric stress, it's either something with the roots (the hot temps) or something off-gassing in your room, like fresh paint or glue. The hydric stress is much more preferable.
And what does turgidity on our plants mean? In short it's the plant utilizing its water and it would mean that your plants aren't dying and still "breathing".
Also nothing to worry about the yellowing leaves, it's just the senescence, your plants are getting old and ready to harvest.
If i was in your shoes i'd give them just tap water or ro until the harvest.