Chicken sneezing and runny poo

I'm not sure, but the link in this post may help you ID it.  The pictures are pretty graphic, but also very useful.

Re: Infectious Diseases of Poultry. in Poultry FAQs and other Information - Page 1 of 1

They were wormed in the last few weeks. I thought maybe the sneezing was due to dust as obviously we've had it very dry. The watery poos maybe because it's hot. Now I'm not so sure. My flakey memory is telling me coccidiosis.

I cleaned the run up, took away bedding and the woodchip floor. Disinfected with Vanodine. Took two days. I do that at least twice a year anyway.

I've used Harkers coxoid in the water before or Tylan yet I'd need a prescription for the latter.

The chicken that has it is getting on a bit. 2 1/2 to 3 years old.

I make my own apple cider vinegar. I use that or garlic in the water.

A broody young chicken has come off her nest and looks exhausted. She hasn't this sneezing thing. I don't know what's up there. I think she may die. I've heard broody hens can do this.

I'm afraid she died. Less that a year old.

Next  time a hen goes broody I'll try and convince her otherwise.

Please have a good look at all your hens.
Check temp under the wings with you hand, check for lice running around under wings, on neck and underneath. Have a look at their eyes, they should be clear, bright and no bubbles. Any rattling sounds when breathing.
What bedding is used?
are the chickens poo good?
Have you any other birds? Do you have open or close roofed runs / any trees above the runs?
Disinfect housing and run area...Vanodine
Were there turkeys present where you got the hen from?