Wasting and a lack of appetite are signs that those organisms have proliferated in their digestive system and so aggravated & swollen their throats that they can't swallow food.
I too need to continue Metronidazole treatments in a tanks where this is suspect. I believe that they were already in the mollies I bought at a club auction, but multiplied when the fish were stressed by being dumped in a bag, toted across the country, put on an auction table and then carried in those bags for another two days.
There are actually several related organisms we call hexamita. They are fairly common, especially in commercially raised fishes. They also are not uncommon among hobbyist raised fishes though. Treatment is the same for the whole crowd of wee beasties.
All the best!
Scott Davis