Are my fish going to die??? Please Help!!!

Hello. I just started a fish aquarium hobby and I have had it set up and running about 1 month. In the tank is 4 rasboras, 3 neons, 7 glofish, 1 betta, 2 dwarf gourami, and 2 rosy reds. I have a 46 gallon aquarium. I know next to nothing about keeping the water chemistry stable. I was told to use water conditioner, which I do at water changes and the initial set up. I also purchased a 5 in 1 test kit / 60 second check of pH, KH, GH, NO2, NO3 tetra easy strips. My betta is not aggressive like most. The only fish that has bothered him was I put in a female betta whom constantly stayed hidden and I found out they couldn’t be together so I gave her away. Now the betta has white spots on his fins and a couple on his body and seems to be brushing against things in an attempt to remove these. Also some of the other fish have 1 or 2 specs but not near as many as the betta. I know this will be a lot for you to address, but I would be greatly appreciative because I don’t want to harm the fish. I really enjoy them. As far as the test kit, it read that all the levels were fine except the water was hard? I am not sure if that refers to the water conditioner. Also I had guppies but they were chasing my other fish so I gave them away too. Can the rosy reds be in the tank? My grandma told me that they release a slime that is harmful to my other fish? If this is the cause I will remove them immediately. I have no live plants. I did have a pleco which I thought was an algae eater that died in the tank. I keep the temperature between 76 to 78 with a water heater and a filtration system that requires 2 filters. I feed them freeze dried blood worms and tetramin or tetracolor. Also the fish have developed slightly fat abdomens? I don’t know the cause of this either. I have looked at some pictures of dropsy and this is nothing like that. More just swollen looking. Any information on the specs, treatment, swollen abdomens, chemistry levels, and additional advice would be helpful. I am at a loss to save my pet fish. Please help me! Thank you, Heather