Chicken has had diarrhoea for a few weeks.

[Omelette-in-progress]

Hello, new to BYC, I'm looking for advice on one of my hens, I've noticed for a few weeks that her droppings have been very watery. She is the only one with this. The flock was dewormed recently and doesn't seem to have any other symptoms, just droppings that are mostly normal in color, just very wet, with the occasional being only water...

I'm just wondering if anyone has any ideas about what this could be? She is a 6 month old Pekin Bantam and has been laying for around a month now.

Thanks in advance!