So - quick update for completeness!! One was very off colour this morning - not eating and 'cough' (what I thought was a cough/sneeze, the vet called a snitch!) had developed into her holding her beak open and looking like she was struggling to breath (which she was) - a 'gape'. Vet advised dispatching for postmortem (as they were ex batt, and therefore vacinated up to the max he said it was unlikely to be any of the common viruses, but suspected a worm burden from free ranging which they were unable to cope with) which he did... and she was chock ablock with gape worm poor thing. Massive things (over 1cm long) in her airpipe. Flubinvet on order. He does not advocate routine prevenative worming though so just said to be on the lookout for symptoms in future and treat. I'd know gapeworm symptoms anywhere now, so lesson learnt. And I guess I can say that free ranging actually did cause this. Makes you think doesnt it. Poor chicken.