Hi don't want to alarm you but with the sneezing and comb color could be a sign of bronchitis I've heard it is making it's rounds keep on with the oxytet and watch for signs of diaherria.If that doesn"t work get some injectible penicillin and use that a friend of mine just had a bout with it and lost several chickens I've been lucky but I vaccinate for it and new castles.
Thanks for the info.
