chicken making funny noises,help

[eeriedee]

hello,i have 11 chickens and my light sussex has started making funny noises like she,s coughing or choking.she,s about 8 months old and have full run of our garden.she seems well in herself apart from this.she may have had a runny pooh.please help..my chickens are pets and im worried especially has now my other light sussex seems to be doing the same.
thankyou dawn