Well are they up side down catfish? lol can you post some water stats?
Size of tank in gallons or litres.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.
How long have you had the fish.
Does he look bloated.
What do you feed your fish.
Swimming up side down can be the fish is dying, bacterial to swim bladder.
Bad water quallity, ph shock.
To many dried foods which can lead to swim bladder.
You need some frozen foods like brimstrimp and frozen daphnia which is good at digesting fish food.
Green veg is good.
Always research the fish diet needs.
Not sounding good if I'm honest.
Is he spending long periods of time on his back.
Does he look bloated.
Any red streaking on his body or fins.
When did you last see him go to the toilet, what did it look like.
Sadly it sounds like he dying to me, they can dart around and heavy breath.
Fish rarely make it when there upside down in the tank.
I would prepare for the worst.
I love corys.
Mine died of old age they can live over 5 years, mine died when it was upside down.
They sound like there dying to me bless them.
Just make sure water stats are in order.
Corys are more prone to bacterial infections.
Sad isn't it seeing them on there backs.
Fish signs when dying are darting, heavy breathing, sinking like there unable to control there balance, laying on there backs.
They sound to far gone to save.
If they look in a bad way might be kinder to put them out of there misery.
I love corys as there so cute, and yes they do make you laugh by there behavour.
They are the best fish I have ever kept apart from my tweety pie who was a fancy ranchu goldfish.