I purchased recently 12 Corydoras C082, newly imported from Colombia (approx. 3 weeks).
I lost 1 last week and 1 today.
Here is a picture of the worst one taken a few minutes ago :

And one that look ok for now :

And complete setup :

They are in a 125g tank.
- bare bottom (for now)
- pH : 7.4
- temperature : 25 C
- ammonia : 0
- nitrite : 0
- nitrate : 5-10 pppm
- Rena XP3 and XP4 canister filter
- 2 Hydro V sponge
- DIY Kaldnes K1 filter
- DIY Aquaponics filter (done yesterday)
I also have 11 Gold Laser CW010 in the tank and they are fine.
I'm trying Seachem Paraguard at the moment.
Only half dose since I have 3 small plecos in the tank (L24, L25 and Adonis).
Do you have any idea what it could be ?
Your help will be greatly appreciated !
Thank You
Chouin