That fish was in bad shape.
What are your readings for ammonia, nitrIte, and nitrAte, using a
I don't think she will make it. Unfortunately euthanasia would be the best option now. My euthanasian of choice is clove oil. Make sure you use a disposable container when you mix the clove oil to the tank water (outside of the tank, of course). Add enough oil so the water is opaque and oily looking, this ensures the fish falls asleep/passes as fast as possible. Make sure its not breathing anymore and if you want to be 100% sure you can freeze it.
If you don't have clove oil there are other ways to euthanize but they are a bit more brutal (bash head/cut head-spine). Freezing is not humane as the fish will feel its body freezing when it is not anesthetized (like the clove oil does as mild doses).
Sorry about the Dojo, I love those guys.
BTW what type of plecos do you have in the tank? Some plecos like the slime coating on goldfish and the loaches and can suck on them at night when they are sleeping to the point of ulceration. Also the temperature requirements for the 3 different species aren't compatible. Goldfish and Dojo/weather loaches are cold-water, pleco is tropical.
do you have any idea how this happened to my loach so I can prevent that from happening to my other ones?