So I’ve had this tank for about a week now and bought these tetra glofish. Now about yesterday one of my pink tetras were having trouble swimming and would just keep flipping over. It finally died. Now this one has just died. There’s only about 1 more fish alive and was wondering if someone could help me identify why the fish died. I had tested all the water and the ph was a little high so I did add a tablet but that was after the pink one died. Any suggestions??