Here are my 5 albino cories I got at Walmart last Monday. 4 appear healthy, but this one's behavior is concerning. He acts like the rest at feeding time, but most of the time he just lies in the corner. Then, he will quickly get up, zoom back and forth in the upper level of the aquarium for 1-4 seconds, and then come back down abruptly to rest on the sand, usually in one of the front corners. His gills may be moving a little faster than the other cories, and he's got a yellowish color to him, while the others are more milky/pinker. What would you do about this catfish? It's been going on for a couple days that I've noticed, and it's rather concerning. Thanks. 29 gal, temp 79, pH 7.5, ammo .1 (the API test color looks between 0 and .25; it's hard to tell), nitrite 0, nitrate 10-15.