Sick neon tetra with white spots!

I just noticed today that a few of my neon tetras have these white growths on them towards the back of their tails. They're still eating and energetic but it most definitely doesn't look nice. Any ideas? I've isolated those worst affected.

I added a BN pleco a few days ago but kept his water out of the tank and he appears to be fine. My water parameters are fine and I've had these guys for over 6 months now.

 

Okay. It's getting worse. The skin and scales are turning black and apparently rotting. More of my neons are affected by so far no other species of fish in the tank is. Any ideas? It's pretty urgent.

 

What's the news on this now? Sorry you haven't gotten any replies yet.

 

Sorry I can't help. Never seen this before.

 

I'm wondering if it's cancer or something similar. It seems to have gone down on the other infected fish bar one who now has them on several parts of his body although some are red. None of my other fish seem to be affected. He still shows no other signs of sickness: he's swimming normally and eating... It's quite strange. I'm inclined at the moment to leave him be and see how he turns out.

 

UPDATE: Whatever it was spread to all of my neon tetras. They look awful for a week or two but then it clears up and they're fine. No other behavioral changes to note. Very odd indeed, I have no idea what could have caused it. None of my other fish seem to have caught it.

 

Good to hear that it's cleared up.