PLEASE HELP LOTS OF DEATH IN TANKS

I think I may have brought a disease into my tank. Ever since I last added my 5 female guppies I have had 5 guppies for two male and three female, and a molly in one tank and recently I think I somehow contaminated my betta tank causing one of my before very healthy bright looking betta to die today. Ammonia nitrites and nitrates are great And Ph is slightly off but not enough at I think it would kill hardy fish like guppies mollies and betta. At first I thought that it was specific to live bearers as my tank has German blue ram and neons in it and they haven’t been affected. And yes my tanks hardness is a little soft but I believe that if tank quality was the case it would’ve affected them a while ago and I’m on month five with my tank now. Every fish that has died has been overnight apart from the betta. And every time I find them they are covered in white spiky slime that goes about half a centimetre thick. But on the molly it was almost a whole cm thick. Every fish that has died has shown signs of dropsy and swim bladder stopped working the day before they died. Or they just didn’t have enough energy to swim I can’t be too sure. The last to die was my betta who usually had a vibrant red and black on him. He feeds only a solid diet of bloodworms and sometimes flakes but him and my other betta are picky with pellets and flakes. I went on a holiday for two days and i knew my fish would be fine as long as the lights were off. Before i left all my pets were fine including fish but when I got back This betta loooed like hell. He is in a divided tank with another’s boy but the other betta looks completely fine his colours are all bright and he is pretty content and full of energy. My red betta looked just like my guppies and molly. I really have no idea whats wrong with my tanks. Not to mention my red guppy I’ve had since day one has started to have flared up scales which seems to be the start of dropsy. I just want to know if there’s is any mistakes I’ve made that I can fix to maybe fix this problem. These were two seperate tanks so I don’t know if I contaminated the betta tank should I move the current betta living there? Also if anyone can help me figure out what’s wrong would really help These pics aren’t of my betta who usually is bright white black and red. A female who was on the verge of death I put in a breeding box with the lid off as she couldn’t swim and I wanted the surface easy to reach and my red guppy who it cant be seen very well but I’m sure is starting to show signs. Please please help me

Could you post the sizes of your tanks and exactly what, and how many, fish are in each one, as well as the actual numbers from all your tests, please? Did you cycle your tanks before you added fish?

A couple of things I can tell you;

Mollies and guppies need hard water to do well, and soft water won't kill them quickly at all; it just makes them susceptible to stress related diseases and organ failure, which might well be what you're seeing with your fish.

Guppies and bettas should not be kept together, they tend to fight and even kill each other. Blue rams need much warmer water than the rest of your fish.

I keep my but ram at 84 degrees, definitely too high for most other fish.

fluttermoth said:

Could you post the sizes of your tanks and exactly what, and how many, fish are in each one, as well as the actual numbers from all your tests, please? Did you cycle your tanks before you added fish?

A couple of things I can tell you;

Mollies and guppies need hard water to do well, and soft water won't kill them quickly at all; it just makes them susceptible to stress related diseases and organ failure, which might well be what you're seeing with your fish.

Guppies and bettas should not be kept together, they tend to fight and even kill each other. Blue rams need much warmer water than the rest of your fish.

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The betta was in a completely seperate tank. That’s why I was worried because it’s a seperate 15 litre tank. My guppies and mollies were kept in a 80 litre tank. The 80 litre at the beginning had 2 German ram, 6 neons, 1 molly, 2 male guppy and 5 female guppy. I don’t have a heater in any of my systems but that’s only because all my tanks are always at either 80-84 and heating it would cause it to be too hot where I live is super hot all the time. My ammonia and nitrites were at 0 and my nitrate was about 10. Ph at 7.2. And yes I cycled my tank before adding fish and it was thriving for 4 months without any drama or death till last month when I added the female guppy.