Diseased Fish? What's Going On

[WeslinCamden]

Alright, so i have a 36 gallon planted tank. Only a few java ferns and amazon swords along with plastic decor. The tank was also stocked with 10 cherry barbs, a gold gourami, 4 cory cats, and a rainbow shark.(I hear rainbows and cory don't get along, but trust me, my rainbow never once bothered one of the corys) When i first set up this tank about a year ago, everything was going alright. I originally had 8 tiger barbs, the rainbow, and a couple gouramis. Sadly i had to give away the barbs as they stressed out any fish i ever put in the tank. All the history aside, I've been having some fish die on me lately and its very worrying. The first thing i noticed was that my rainbow was hiding for almost 2 days, and once i finally saw him i noticed something was very wrong. His lips were swollen and red, and one of his eyes was bulging as well as lethargy. I realized he was sick so i set up a quarantine tank the next night for him, but in that one extra day his eye had swollen drastically and the next morning i found him deceased. (A huge bummer considering i've had him since the beginning of this tank 

) Anyways i kept scouting out all the other fish for any pop-eye or other weird symptoms, almost all looked fine but i noticed that one of my male cherries was getting pop-eye and hiding down by the bottom of the tank so i put him in the quarantine tank as soon as possible. But sadly he didnt make it either.. This was yesterday. Ever since, i've been meticulously watching the tank for any weird symptoms, but strangely there was nothing weird and surprisingly the tank seems a little more active. There was hope i caught this in time. If only that were the end of it... 

 To my surprise i just found one of the female barbs dead, when i removed her from the tank i noticed she had guts protruding out of her belly (Maybe an air sac? It was a single organ) And since she couldn't have been dead much longer than an hour, i doubt the other fish chewed her up. So here i am now, very paranoid and clueless what to do. When getting some supplies for my quarantine tank, i asked about melafix or pirafix, but everybody just suggested some "good ol'e" aquarium salt. However, at this point i think its beyond a wounded fish or two and something must be going on. I do a 25% water change every week, and my water parameters are and have always been perfect (Aside from higher hardness from our regions tap water and a pH of 7.5) So now im looking for some advice from people who actually care about the fish and not the profits made by them. I have a few ideas what could have caused it but i would like some input.

1. I added 2 cory's about 3 weeks ago, and 3 male cherry's about 2 weeks ago. I did not quarantine them (I noticed no symptoms or symptoms from any other fish in the tanks)
2. 1 of those cory's died the day after putting it in the tank (I assume from shock) and didn't noticed it until a day later, So maybe it decayed and polluted the tank or something?
3. 1 of my ferns, and 1 of the swords were introduced about 3 weeks ago. I'm not sure if they can carry anything serious, im just speculating.
 
Those are really the only things i can think of, but i would GREATLY appreciate any speculation or ideas on this. I've never had a sick tank ever (Aside from the occasional ich in a new setup) so i'm really at a loss on what to do here. Any input would be greatly appreciated! Thanks!

 

[WeslinCamden]

URGENT UPDATE: I just found another cory dead! And I noticed a small white patch on my gourami's head... What is going on?! I'm going to go buy some medications tomorrow, does this sound like Bacterial? Fungal? Parasites? Only things i forgot to mention was that i put in some driftwood from a local lake about 3 weeks ago too, but i boiled each piece for almost 2 hours. I've also been getting some micro-bubbles, doubt thats causing this but i want to be as detailed as possible.

 

[Munroco]

I don't know what's going on with your fish, but until you find out I'd be wary of using meds. Can you tell if the latest dead cory was one of the new ones? Its possible if both the dead ones were from the new lot then they came with something wrong with them. Other than the cats its possible that the other deaths were not related.

 

[WeslinCamden]

I want to say that they were both the new ones, but im not sure. My original two cory's were inseperable and the two left are just as well so im hoping that it was because of the new cory's and that maybe my rainbow and male cherry injured eachother from chasing around and got infected. Either way i havent seen any changes today and the tank is pretty active. Ill continue to do a 15% water change daily for a week or so, with hopefully no need to make another post.

 

[WILDER]

It sounds bacterial to me.
 
The patch on the head does it have a spot in the middle of it?
Any red or pink areas. in the centre or outside of the patch?
Any dead white tissue around the edges of the patch?
 
Can you post your water stats please.

 

[FishLover1996]

white spots or patches usually means ick but I honestly have no clue about your other fish. I'm so sorry

 

[Far_King]

I'm not sure quite what's going on in the tank but it sounds like the last fish you added may have introduced something.  Sadly this is a problem many of us have encountered and as you now have a spare tank set up, I'd advice quarantining any new additions for around six weeks in there prior to adding to your display tank.
 
The dead fish that was in there for a day would not have polluted the water in that time.  You're doing the right thing in keeping an eye on everything and I do head counts on my tanks on a daily basis.
 
As you've identified a variety of symptoms , perhaps have a look here http/www.fishnet.org/sick-fish-chart.htm andsee if any fit.  It sounds to me like a bacterial infection but it's difficult to advise how best to treat at this time