help hen is like wheezing

[chicken ridl]

I have an Americana that I have had since it was a day old.
They havent even started to lay yet.
I noticied a stange noise from the pen and whatched the girls to see what was going on.
I have one that is making a strange wheezing like noise.
And her mouth is open when breathing.
What could that be?
This is bad because I have around forty birds and all but the 10 americanas are laying. They are all in the same house in separate pens. Need help ASAP !

 

[eggsrcool]

Age?
Date last wormed?
Type of bedding in use?

Also,

 

[chicken ridl]

They were day on June the 4th
I have not wormed them.
Thay are outside on dirt and grass in the pen and the barn
has a wood floor with straw.
They have been in there since day 1
Mater of fact they were raised in that same pen with 50 cornish rocks that are now in the freezer.
This just started yesterday or today. Did not notice anything Sunday. Thankyou for your interest. I am not sure what is going on I have never had any health problems with my birds.
I did add 5 white leghorns about 5-6 weeks ago.
And I had them quarantined for over a month. They are showing no problems and the 5 roosters that came with the 5 hens are still in the other pen and showing no problems.