Hen with red swollen bum and not laying

[Ruby Mia]

My x battery hen has still got a bold, what looks swollen, bright red bum and isn't laying. she hasn't got worms, and she is acting normal, any ideas what this is?

 

[ten chicks]

My x battery hen has still got a bold, what looks swollen, bright red bum and isn't laying. she hasn't got worms, and she is acting normal, any ideas what this is?

Any whitish discharge,if yes could be vent gleet.

 

[Ruby Mia]

there is a little, but not much. Also I just spotted her in the nest box, so she could be starting to lay again.