About 6 weeks ago I acquired 4 small clown loaches, each about 2-1/2" long. They have all been doing great until recently. Up until about a week ago, they have all been very active and were eating great. I would drop in some algae waffers and bottom feeder pellets and they would be all over them, pushing their way around competing with my corys for the food. They would be clicking away as they ate. I also put in fresh zucchini, which they would gobble away at. They were also very active, zooming around the tank stopping only long enough to do their "loach dance". Now in a few days time they have totally changed. They seem to have no appetite, and just sit or lay on their sides under a rock ledge. I see them swim out every now and again, but their behavior has totally changed. I've done nothing new with the tank such as adding more fish, etc. Just not sure what could be going on here. This is a 55 gallon tank and I do 2 50% WC
weekly to try to keep water quality as good as possible. Water params are all good. Any advice?