plant issue, curling, yellowing.

so i am having some issue with these. one has a stem that is cracking, most are showing yellowing. one has gotten really bad with some darken edges around the yellow spots.

its a confined space, so i am thinking that heat may be playing an issue as well. some help in the right direction would be very useful, thanks.

so anyone got some idea's?

one more try with a bump

you def have heat issue. when leaves curl up on the edges it means there struggling to keep cool. yellowing could be from this too maybe im not sure but i know you need to get temp donw some. whats it now?

it sits at around 28, i know a bit high but i was able to get it down from 30 so far. so im going to keep trying to get it lower, thanks