yoyo loaches dying

Question
I've got a 55 gal freshwater that's been set up and happy for 1 year. Current inhabitants include 2 angelfish (1@8months and  1 introduced 2 days ago), 8 panda cories, 4 otto cats & 3 yoyo loaches until this morning. I found 2 of the loaches dead this morning and now the 3rd is acting sick. Rapid breathing and lethargic movements. I changed the water on schedule right before I introduced the new angelfish. (30%@2weeks) What should I do to help this little guy. I never noticed anything unusual w/ the other 2. They were swimming as normal last night. But thier scales were coming off as I pulled them out of the tank this morning. I don't see scales coming off of the last one but it's definantly struggling.

Thanks

Answer
Considering the new addition of the angelfish I would be suspect of him first. Watch them and see if anyone picks on the little guy, especially the new angel. If that leads no where it would be best if you could remove him to a hospital tank as he should be treated and the other fish should not recieve treatment unless they are sick as well. Get an all-in-one fish treatment, as your description does not narrow down any specific disease, and treat the little one following the directions. Next, only change the water every 4-5 weeks. If you have to change more often you do not let the natural bacteria in the tank help to create the natural ecosystem it can. I hope this helps. Let me know if you need more help.