Spotted Pim Catfish...

[NjFabianoWNY]

Hello. I have a 46 gal tank.
Sand.
Planted.
About 10 fish.

Problem:
I have two spotted pim cats.
Over the last week or less I have noticed one has began losing color and turning a tiny of yellow.
The other looks normal.
No behavior difference noticed.

Background:
They were almost the first species I put in the tank.
My tank has Been running for about 4 months.
Nothing has been added or changed in the tank since I noticed the loss of color....


Ideas? Should I be concerned?

Ps. Water tested at least weekly. Seems fine except small (.25) amount of ammonia from time to time.

 

[NjFabianoWNY]

I've also just noticed my female sword tail is gone from the tank. Unsure if that's related.

Could the pim cat of ate the swordtail?

Both 2 to 2.5" in size.

 

[NjFabianoWNY]

Looks to be getting worse and lays around all day.

When I drop food in he goes just as crazy as the Pim catfish always have/do, but then after feeding goes back to laying around.

Still really losing color/tinting yellow