Sick fish, grey patches on mouth & body

[Kirasouza]

Hello everyone please help I already made a post but didn’t get much interaction This fish started sitting at the bottom for a couple days and acting very strange but it would still come up to eat and then he started drastically looking really sick the last couple days his fins are looking Ridgid he looks like he has some type of white some thing on him his mouth is white and also looks like grayish white spots patches on his body hes doing this really weird thing with his mouth and like almost looking like he was having a seizure I was trying to do the salt and heat treatment and it killed one of my pleco n snails so I’m not really willing to do anymore more salt I don’t want to kill my big pleco I tried ich treatment at first but I don’t think it’s Ich and it didn’t help yesterday I grabbed api melafix  because from what I can see it looks like fin rot but then I saw another post on here and somebody posted a fish with velvet and I’m thinking it could be that also does anyone know if they can tell me what it is? And what should I do my other fish look fine except my red cap oranda did pop up with a couple black spots but he’s the most active and “happy” but they are kind of starting to sit at the bottom too I don’t know if they’re just sitting with him  also I previously had a 20 gallon and my nitrogen cycle had completed I had recently just got this one it’s a 40 to 50 breeder tank I think from adding so much water my nitrogen cycle got messed up so I pretty much am also having to completely restart that as well and do a fish in cycle what should I do i’m doing Melafix right now I think tomorrow I’m gonna try to get pimafix and do the both of them will this fix my problem also because I had to restart my nitrogen cycle during all this now I’m in the middle of the melafix and it says to wait seven days for a water change and now I’m having an ammonia spike it’s at .25 should I do a mini water change still

Also I wanted to add that I did do a salt treatment before finding out that plecos cannot handle salt and now my common pleco is looking all white and his eyes have some thing over them and look slightly bloody I feel so bad he’s so big and beautiful and he’s survived so much I rescued him I ordered Stress coat that will be here tomorrow so hopefully that will help

 

[Fae]

Water changes won't wreck your cycle. The bacteria lives mostly in your filter. Did you transfer your old filter media into your new filter? That's the easiest way to start a new cycle in a new tank, often instantly.

Do a big water change to get as much of the salt out as you can. Look up columnaris (you can click the word columnaris, it should have created a link), sounds like what your fish might have. Keep a clean tank the best you can to help your pleco heal. A piece of wood would also do wonders for it's health if you don't have any, they eat wood and will basically live on it once it's in there