Ich Question

[Scales9]

My husband bought home 4 plays last weekend, he was floating the bag in the tank and we were having a good look at them one of them had a small white dot on her tail so we played it safe and put them all in the quarantine tank, it has been a week now of heat salt treatment and the one small white dot is still there,nothing els had appeared, my question is if it was an ich spot should it have fallen off by now, I had ich in my main tank but different fish were being affected at different times and it took 2 weeks to treat the whole tank.

 

[FishFanatic04]

Maybe it's fungus?

 

[Scales9]

Maybe it's fungus?

Would a fungus grow bigger though?

 

[Scales9]

So I have had the platys in quarenteen for 2 weeks now and one still has a white spot on her tail fin, can I now assume this is just a marking on her tail? I was thinking ich but thought that if it was the spot would have fallen off by now.Any ideas???