Nothing ruins a reenactment weekend like ill-fitting or soggy footwear. Once the correct fit is established a liberal coating of your favourite waterproofing prep will help a bit to keep water out. And ALWAYS carry a spare pair of socks.
On the other hand that fungus probably is somewhat akin to a period affliction of some sort, which could take us all a step closer to an accurate historical experience!
If we did period accurate we would have to infect 1-1/2 soldiers with dysentery or something. Period accurate diseases only please.
My back pain can fill in for Rhoomatiz.