I'd be giving the vitamin E, also. And, yes, they may need antibiotics/more antibiotics. Darn.
I can't imagine where they picked this up, unless it was off the shoes of a visitor, or maybe it's was weather and stress based? You've had people there working, and they may have been stressed about it?
Was there dust from the work?
I'm sorry to hear this. I'm praying that everyone gets well asap. (((Hug!)))
Love All Life, Thank You For Posting! :)