cory catfish injury

Please help in identifying what happened? Yesterday she was perfectly fine and happy. I did do a water change yesterday. And woke up to my Cory looking like this. I think she is going to die but I need help in knowing what happened. Is it a heater burn? Or something else. I'm so very sad as I've...

Hey guys I’m very panicked right now I woke up and some of the male guppies on the right side of my 29 gallon somehow got onto the left side past the divider with my female guppies and beta and well i can’t find the hole in my divider so I think they might be jumping over the top of it. I put...