Lemon Tetras dying
My lemon tetras seem to be slowly dying one by one. It seems that they seperate from the school and then once I find them they are having trouble swimming. Their bodies are curved and they cannot stay up in the water; they float down to the bottom of the tank all curved and sideways. I am not sure what is wrong with them. Also, it seems that it is just the biggest of the tetras, the smaller ones seem ok.
Here are the tank specs: 29 gallon, 8, now 6, lemon tetras, two Bolivian Rams. The tank has been running for a little over two months and is cycled. It is fairly well planted with two large swords, about 40 dwarf chain swords, two small Vesuvius swords, and a small amount of babys tears. The temp. is 80, ph 7.8, ammonia 0, nitrite 0, nitrate 0, KH 8, GH 17. The fish are fed a good quality flake food and they have been in the tank for about 1.5 weeks. All the fish came from a LFS with a good reputation and no sick fish in the store tanks. They were all introduced at the same time and water quality was monitored.
Any ideas as to what is killing them? I have another lemon tetra now swimming at the top of the tank gulping air and I fear this one will be next. Any help will be appreciated.
Oh, I do not use CO2 for the plants.