Broken fin? Finrot? What is this? (pictures)

I've been having a really unlucky streak lately, my god!

The fish's left fin looks like it's broken. There's a swelling around the base of the fin with some white skin that kinda looks like chalk and the left gills looks red and swollen. Some of the head's scales kinda look ruffled.

I lost my largest adult Rainbow Boesemani a few weeks ago after hearing a loud BANG against the lid of my tank. The next day, Its left side looked red-ish and damaged as if it had scratched its side against a rock so I figured maybe he slammed against my lid and injured itself. I noticed that my male blue Boesemani seemed quite active and actively following other fish so I wondered if it could be a bully.

None of my other fish look like theyre having problems, although I added 26 baby Cherry Barb about 1.5 months ago and lost about 15 of them. I also recently lost an adult cherry barb to Dropsy. My problems started when I did a filter cleaning and tank cleaning roughly 2 months ago and accidentally left the syphon, causing a minor flood but ending up emptying roughly 50-60% of my 55 Gal. I was wondering if this could have killed way too many bacterias and caused a new cycling.

I do a 20% water change every week.

 

I also just found a zebra danio dried up in the corner of the room aghhh! What is going onnnn

 

I also just found a zebra danio dried up in the corner of the room aghhh! What is going onnnn

As i a jumper?

 

As i a jumper?

yup! I'll lower my water level from now on I supose, its been a rough last 2 months xD I've been doing this for about 3 years now and over the last year things were going fine until suddenly I started facing problems

 

yup! I'll lower my water level from now on I supose, its been a rough last 2 months xD I've been doing this for about 3 years now and over the last year things were going fine until suddenly I started facing problems

We all seem to get rough patches at some point, for sure

 

I THINK I HAVE A BULLY. I once again heard a big BANG and rattle from the tank, I only had time to turn around and seen a lot of fish swimmign VERY FAST and the fin looks a bit more damaged too. I don't know which one it is but I suspect the blue x.x What do you do in this scenario? I dont have a second tank to isolate a bully.

 

I freaking SAW HIM, the blue Boesemani suddenly dashed and attacked one of my red boesemani in front of my very eyes. I was already suspicious of him since my big Rainbow Boesemani died. I think he's been stressing out my fish for months now. What do I do with this jerk?

 

Possible to take to an LFS? Otherwise might have to set up a breeder net or breeder box ASAP to isolate.