Droopy hen

I'm at a bit of a loss as to what to do with my cuckoo maran hen. She is one year old next week, and came into lay in March. She started recently to walk around with her tail pointing down. We discovered she had some lice and they were treated and went away. (The other hens in my flock were either not affected at all by lice at the time or had at most a very minor infestation - the maran was very badly affected, which was a shock as it come on very quickly.) We did wonder if she might be walking strangely due to discomfort, but the lice were cleared up and she did not improve. She continued to walk around with her tail pointing down, but was enthusiastic about her feed (she is a well built bird!) has a red comb, laying 4-5 eggs a week. Then in the last week she has started sitting down a lot - she will walk over to her food and sit down beside it and eat there. She is becoming more droopy. There are no other symptoms.

I don't know if I am being paranoid, but the only thing I can find which has 'droopiness' as a symptom is Marek's disease. The hen, as I said earlier, is 51 weeks old. I have a small flock of only 13 hens, 3 of which (including the maran) were hatched at home, the others have been bought in 2s and 3s from good sources.

I also have a broody hen sitting on eggs at the moment - if it is Marek's disease, I am aware the maran will have to be culled, but what factors should I be aware of with the new chicks?

Hi It doesnt sound like Mareks, is she laying at the moment? If she hasnt this could  be where the problem is. With Mareks it is more of an inbalance as apposed to droopiness, you can sometimes see a distortion on the pupils where the nerves are affected.
Check her poops how do they look?
Check her vent -does it look swollen? Is her tummy hard?
And as Cathangirl suggested check the tone of her crop in the morning - does it feel largely empty (normal) or hard/sqashy and is this different to the other hens?
Check for redmite in the coop as well, this can lead to severe anaemia in poultry, particulary if they are already under the weather.
Good luck and please keep us posted!