Thank you so much for your replies and the link: very interesting to read. And Scary!!
I am not sure they have been wormed: I bought them from a breeder 3 or 4 weeks ago and assumed he would have taken care of this. I will contact him.
Her breating doesn't sound rattling from nearby when I am in the run, but I will pick her up and hold my ear against her chest. That will probably tell me more.
About the ventilation: When I bought the pen I thought the 'nightbit' was to open for the weather: the place they came from was very 'sheltered', but with me they are in the garden. The day I got them we started to have wind chill's -10 degrees Celcius so I hung a teatowel in front of their entrance. Maybe I should remove this? There is a little door on the side: when it gets warmer, do you think I should open this for some extra fresh air?
I will try to attach a foto so you can see the pen. (the blankets are because the wind chill, which is over now so they are gone).
I am glad to hear she is playing
it does look like it but I have never seen this before with chickens. She makes me laugh all the time.
As soon as I open the back door she rUns towards me, tripping over everything she should have noticed being there but didn't and this includes the other chicken!
When I get into the run at 'bedtime' she hops on top of my shoes and sits there all cosy and comfortable
Because she is so active I put things in the run for her to jump on top and peck at so she doesn't get bored.
I would hate it when things would go wrong just because I didn't do the right thing. I grew very attached to her over te past few weeks
What if I lift it over the weekend and if things don't improve I can take her to the vet, or should I give her a week's time to recover?
(My attachment is too (to?) large: I tried to make it smaler, but this wasn't enough..)