Being hairy and thin in back end are also signs of worms.
I'd be tempted to worm them anyway won't do any harm especially if the cough isn't in conjuction with high temp or other outward signs such as not feeding, being lethatgic etc.
Also check air flow thor your ark, we have drilled two inch round holes in the apex of our arks to allow air flow thro, it doesn't make it draughty but lets air circulate, pneumonia can be a problem with all this cold damp miserable weather we have been having.
HTH
mandy
Ps

for getting GOS welcome to the mad world of the GOS!