Don’t understand

Hi Pinheiro.  You can’t see the chicken in the picture, but the poop doesn’t look like any particular disease as far as I can tell.

If the chicken is sitting hunched up, it is ill but it could be something as simple as worms.  If you can supply more details we can try and help.

Is the chicken eating and drinking?   Has it laid any eggs recently?  Have you picked it up and notified anything like thinness or lumps under the skin?  That sort of detail is needed