Hi,
Your tank is a little os, but I don't think thats the reason he died.
When did you last clean the water?
The main problem I see is you only have one Cory! Cories need to be kept in groups. Sometimes Cories can die of lonelyness.
Cory Lover
indeed. cories should be kept in groups. I recently lost one of my albinos, so i am down to 3. I think i will buy a couple more at least to make them more happy.