We are going to need a lot more information in order to help you out...
Let's start with your water stats - ammonia, nitrite, nitrate, PH, tank temp ect. How often do you do water changes and what percent of the water do you take out?
What was your newest addition? Im assuming we are talking about the tank in your sig - if not, please tell us of the other occupants of the tank and it's size.
How long have you had the loaches, how big are they? Is any other fish showing any signs of illness - any flicking, swimming issues, spots or marks on the fish ect.