Sores on Tetras?

Hello, Two days ago I added 5 Rummy-nose Tetras.
3 of them acclimated great and were doing great, the other 2 were completely pale and not swimming much. The next day I found the 2 dead with these open sores on their bodies. I assumed the sores were from other fish trying to eat them. But, today I wake up to find one of the tetras still alive with the same sore on it's body! I have Oto's in the tank and I have heard that Oto's will suck on slow moving fish. But, unless something else was wrong, wouldn't the tetras be able to get away?
I also noticed one of the Tetra's has what looks to be a white, fuzzy growth on it's side. Could this be what is causing the deaths?
Thank you so much for your help!

NOTE: These pictures are of two different fish. The two fish that died had the sores on the same part of the body as the fish below.

UPDATE: Fish with sore on body is now having a hard time staying upright. Spine is bent where the sore is. It is now laying on side. Will die soon.

 

What are your Ammonia, Nitrate, Nitrite and pH?
I took a look at your profile, it looks like this is a new tank. How long ago did it finish cycling? Fishless or fish in cycling? And how far apart did you spread the addition of new fish? It sounds like maybe you added too many fish too quickly and had a minicycle. How are the Otos handling this? They can be a bit on the delicate side.

 

Ammonia:0.25ppm, Nitrite:0ppm, Nitrate:0ppm, PH:7.2

it finished cycling about a month ago. The people of Fishlore said that all my live plants were eating the Nitrates but that it was definitely cycled.
My Oto's and Platies are doing perfectly fine and acting normal. It's only the Tetras.

 

How far apart did you add all the fish?
And I'm glad the rest of your fish are ok. It still sounds like it could be a minI cycle to me.

 

1-2 weeks apart. Monitored the water everyday. No ammonia or nitrite spike.
The ammonia would have to be really high to cause burns like that. And a minI cycle doesn't explain the fuzzy growth.

 

Ok, I didn't realize you tested your water that frequently, that is great. Hopefully someone else can jump in with suggestions for what can be the cause.

Also I was thinking that poor water quality can cause fish to be stressed and therefore more suscerptible to fungus or other diseases. Since your water quality appears fine at least you have ruled out your cycling as the source.

 

Thank you for making sure that wasn't the cause! I'm sure a lot of people don't think of that at first.

UPDATE: The fish with the sore has now passed. The fish with the fungus looking thing is starting to lose color and is just resting at the bottom.

 

Is there a way you can set up a quarantine or hospital tank for the affected fish? If you do figure out what it is, it might be easier to treat only the fish that are sick. Plus a quieter tank might help with recovery. I will see what I can find for possible diseases and treatments.

Does your LFS have any kind of health guarantee? I know my LFS has a 14 day guarantee, as long as you bring in a water sample and the death was not due to water conditions, improper care, or poor choice of tank mates etc. Basically as long as you were providing an adequate environment for them. At the very least I would check back at the LFS and see if the other fish from the same tank are exhibiting the same symptoms, and ask the LFS staff what they are treating with if it is. Also, if they offer to replace them, see if you can pick them up from a different tank and at a later date, once all symptoms in your tank have been resolved for a few weeks. I would freeze the fish you lost too, and just hold on to them for now.

Update: take a look on here and see if anything fits the symptoms.
https://www.fishlore.com/Disease.htm
Maybe you can request help from the author?
Maybe also look up hemorrhagic septicemia, could be what is going on.

 

Thanks for the advice!
I actually went by the shop I bought them at and all the other fish were perfectly fine! Turns out, they had just been delivered to the store minutes before I bought them. So, they must've been super stressed. I'm assuming that is why they passed. Having been in three different waters in the matter of an hour. The store owner was very nice and replaced the three fish.
When I got home the one fish with the fungle infection (I am assuming that's what it is) was swimming around and got his color back. So, I picked up some Pimafix and am going to dose the entire tank. I don't think he'd let me put him in Quarantine if I tried, he's too busy playing with the new shrimp I got!