whats wrong with my hen?

i think, no, i know one of my hens is poorly but im not sure whats up or how i can help her.
She looks dreadfull her feathers are all raggidy, she sneezes a bit has a snotty nose, (like my kids when they had a cold).
She IS laying practically every day more often than not the eggs are almost perfect but occationally she lays a wrinkly one ( well i think its her). She is eatin and drinking and keepin up with the rest of them. All the other hens seem ok, one has sneezed a little but no disscharge and i did have to put another one out of her missery this week cause she was NOT ok not eating or drinking.
Now i dont want this one going the same way if i can help it. These are not pets but at the same time i dont want her to suffer.
Anyone have any ideas?
Thanks
Dawn xx

Straight to the vets - any respiratory virus will spread throughout the rest of the flock quite quickly - I speak from bitter experience here  A dose of antibiotics should hopefully clear things up, but you do need a vet's advice on this.