Weird acting Swordtail

Hi,

My female Swordtail acting very strangely on the past few days.
she doesn't eat very much(or not at all), staying on the bottom of the tank. I got more 4 Swordtails and they seem to be ok.
My tank is 100 litters, it's community planted tank with Guppies and Cories.
All water parameters are cool( 0 ammonia nitrites, 20-25 nitrates).
There is on sign of injuries or fin rot or white spots on the fish..( I attached so pics).

Any idea?

A picture of the whole tank please. She looks a little scared, Swordtails like lots and lots of plants especially floating plants. Their mouths face upwards, so they want to be on the surface of the tank. If you don't give them surface plants, they will think that a bird will eat them, therefore they will sit on the bottom of the tank

itiwhetu said:

A picture of the whole tank please. She looks a little scared, Swordtails like lots and lots of plants especially floating plants. Their mouths face upwards, so they want to be on the surface of the tank. If you don't give them surface plants, they will think that a bird will eat them, therefore they will sit on the bottom of the tank

Click to expand...

She is hiding behind the rocks on the right corner

Cool tank, less air please and floating plants. All that air movement will be upsetting her.

itiwhetu said:

Cool tank, less air please and floating plants. All that air movement will be upsetting her.

Click to expand...

There is only bunch of floating tank on the left corner. I will decrease the air pump bubbles.
But do you think the Swordtail got an infection or something?

So just to be on the safe side, I put her on quarantine tank with aquarium salt and keep watching her.