So I have 2 clownfish whom I had for some time now. One is much bigger than the other. I did a water change yesterday and they seemed completely normal up until when I got home earlier today. This morning they were completely fine, but later in the afternoon I noticed that they were staying in the middle of the tank and swimming a bit slower than usual, I also noticed they were breathing a bit faster too but I didn’t mind it at all. I got home 3 hours later and found my smaller clownfish on the sand leaning against a rock struggling to swim and still breathing fast. The bigger clownfish moves up and down the tank but in a slow manner and when she goes to the bottom she too tends to lay against the sand a bit. No visible signs of any disease but I did notice the smaller guy’s face is kind of discoloring. Besides that they seem to be completely fine physically. What do I do?