hey guys im new here, i have a 15 gallon hexagon tank with small gravel, a fake log and some fake plants I hope to get some live plants and a Q tank soon but can't immediatly. I've had my aquarium set up ab a lil over a month. a top flowing filter a heater keeping the water between 72-80. I started out with 5 guppy, 3 male, 2 female. woke up next morning after putting them in the tank 1 male was missing, then 1 famale and 1 male so i went to petco they oked the water and we brought 3 glass catfish with eventually died. then I got 1 more male guppy and he died, leaving me my origional 2 males and 1 female, i recently bought a 4 inch dragon fish, ab a week after that my female started swimming more labored, hard breathing andonly one gill was moving and her eye was buldging and cloudy. sooo now i have 2 male guppy and a 4" dragon fish. my dragon fish seemes to be very active and I haven't seen him eat any of the shrimp pellets i put in there. my guppies seem to be happy so im at a loss. help what am i doing wrong