Hey yall, im new here and to the aquarium world and just got started with a tank that was gifted to me about three months ago. Now the tank i recived was an already established 29 gallon tank and came with a green tiger barb, a cory cat, and two plecos. My girlfriend and I set the tank up and had no issues for the first month of owning it so we decide to add some fish. We went to a local pet store and picked up two tiger barb because we felt having the green he would enjoy some company. Well after about a week of bullying and fin nipping the new barbs around the green became sick and died of what i now belive to be fin rot. We found one of the plecos sucking on the dead barb and within that week that same pleco passed. About another week after that the two new tiger barbs died. Throughout the whole process of owning this tank i have cycled about 25 to 35% of the water every two weeks and consisantly check the ph, ammonia, nitrate and nitrite levels. Ph is generally between 7.2 to 7.6 ammonia is between 0 to 0.25 nitrate between 0 and 5 and nitrite is about always 0. We have gone about two months now with the same cyclingroutine and havent had any issues and thought we should try again. We went to a fish specific store this time around and picked up another cory cat and a rainbow shark three days ago. The cory has done just fine but our RBS has died today. In the three days we have had it it didnt eat flake or pellet food and spent most of its time swimming vertical nose up against the glass. Now am i doing something wrong or did i end up with some bad fish. Any help would be appreciated. Thanks!