There is something going on.
Looking over the reviews the H100 should be able to get something close to 12C rise above ambient temps. source
If your room is 75F (23.8) and add 12C to that - you get ~36C. Which is what you were getting.
-> So - you only need to figure out what is different now.
Did using the compressed air end up blowing dust and debris into the Rad, maybe?