Poorly Girl?

I wonder if anyone can help? My blue Orpington Molly has not been herself since early summer.  We had that hot spell and she got frothy eyes so the whole bunch of girls were on anti booties for a while which did the trick. Both orps went off lay and Molly still hasn't layer since. She has jus been through her moult but her comb is still palest pink. They have all just been worked with flubenvet. However, this morning Molly is making a funny noise every time she breathes in and out. She will have the odd sneeze but that is it.  What is wrong with her? As I said she hasn't been completely right for a while. Although seemed happy, eating drinking and running around.  Any ideas great fully received.

Thanks Joyfull. Does that mean they all need treating again? It was 12 weeks after the treatment that we could use the eggs and they have only just started laying again (except for Molly).