In the 18 plus years I worked taking care of a large and diverse amphibian collection with vets on the staff, we saw a number of "similar" lesions (for lack of a better word) across multiple taxa during that time frame. They ranged from injuries, to encysted parasites (if they are encysted they don't show up on a fecal and the resulting infection can take a significant period of time to occur), to secondary infections from viral or fungal agents to abscessess that were deeper tissue and looking for a way to drain to the outside of the frog. Often the biopsy showed multiple pathogens infecting a site (potentially including fungal hyphae and/or protozoans (in the case of aquatic animals) or on occasion a piece of sharp material that was embedded in the tissue.
While I have not tried the cold chamomile tea, it was discussed a couple of times as a potential option until the cultures and the sensitivities came back from the vet techs.
Ed