Urgent! Bloated Dying Cory

HI all so I woke up to find one of my peppered cories ballooning and laying on its side in the corner.

In the past month, I had 2 other cories die: the first peppered cory died when I was on vacation and I did not know the cause of death. The second sterbaI cory turned very pale (like it bleached itself) before dying the next day.

History of the tank:
Last added 5 more sterbaI cories after 1 month qt on july 20th
Prior to that the last fish added was an angelfish in february.
2 months ago I had several discus die in the same tank but without any visible symptoms (view link)
Unknown Fish Deaths

Parameters are looking good and no other fish looks ill.

I will hazard a guess at 1 of 2 things: 1) I fed the tank shrimp last night, which my cories LOVE, is it possible he ate way too much and is simply constipated or can't process all the shrimp? 2) internal bacteria is making him swell up.

Please help!

 

worms ?
Doesn't loik that bloated to me.
What do you feed ?

 

worms ?
Doesn't loik that bloated to me.
What do you feed ?

Thank you so much for helping!!
It might be the the perspective of the picture, but he is definitely very swollen. At least compared to how he was yesterday.
I feed them wardley pellets as a staple and every other day either bloodworms or beef heart (though they usually the other fish eat all the beefheart before the catfish can get any). I also throw in veggies (for the snails) or if I'm cooking something I think theyd like (like the shrimp yesterday).
Ive never delt with worms before, if it is worms how would you recommend treating?

 

Mmmm did you recently fed them beefheart? The protein in beefheart isn't a right one for Corys and seems to be hard or even not digestable for these friends.
Starting to think that might be the issue.

 

Sadly the cory is dead

DoubleDutch I did feed them beefheart last Saturday. Do you really think that was the issue? Ill have to find a way to feed it to my discus without letting the cories get it then 0.0
Thank you for you help!