Leaves turning brown & deteriorating PLEASE HELP!!!!!(SEE PICS)

Ok here we go... The 1st problem that I'm seeing the most is the browning of the leaves that's in pics 1 2 and 4. The second issue which is on 2 different plants is entire stems dying (pics 5-6) but not to a crisp where I can pull them off, and the 3rd issue is the deteriorating of the leaf which is in the 3rd pic. Other than those issues the plants appear to be growing fine and healthy for the most part with the acception of a few older fans yellowing or dying... I'm at 2 1/2 of 12/12 I didn't feed them bloom nutes until about the 2nd week in which I'm using earth juice bloom and meta-k (normal dosage) and a little monster bloom. As you can see I'm in a homemade green house (don't laugh) in which I'm inducing the night cycle by covering it up for 12 hrs with a black tarp. On sunny days the temp jumps up quite a bit (90s) because my room is holding heat for some reason (possibly the white plastic?) and at night originally the temp came down but the humity rocketed to like 80% that is until I added the inline fan in the pic which brought it down to like 60%. so that's bout all I can think of that would help in the diagnostics if it's anything else u need to know just ask I'm open to all input and suggestions so please help me out as best you can... Thanks in advance you guys never let me down...​