I was looking in my platie tank again, I have just found 4 babies in there, when I notice that my sunset platy has a HUGE chunk of her top fin missing. There is a bit of whitish fluff coming off of her back too, its very tiny and wispy. I seperated her from the rest of them in a 1 gallon bowl, that I know is not big enough but my QT tank has a betta fish in it right now.

She has thin white stringy poop, so does Eleanor. Thats a bacterial infection right?
Other then the ripped fin and the fluff shes fine.

I don't know what to do, should I medicate the tank? If I do will it kill the babies?? They are in a breeders net on the side of it. Im scared that they all have Columnaris again. Eleanor had it when I bought the bunch of them, and Im scared that she may get it again.

If anyone has any suggestions PLEASE let me know. Otherwise tomorrow Im whipping out the Maracyn and salt, and pray that the babies make it. I have no where else to put them but the 1 gallon bowl, and its not going to be warm enough for them.

Columnaris is pretty hard to get rid of but you could try adding salt up to .2% add the maracyn and lower the temperature.
Whats the temperature at now and does it fluctuate?

You have to seperate the sick fish as well

I know to salt and use maracyn, i have allready seperated Madonna. Im more concerned if the rest of the fish get it, can I medicate the whole tank, or will the babies be hurt in the process?

The temperature of the tank is currently at 75 and is normaly in the range of 73-76. It only fluctuates to the lower temps when we leave the windows in the room open to cool it off.

Madonna is not in a good way right now, she let me touch her, the white fluff is visible in her mouth now. Im gettting out my old 4 gallon tank and setting up an emergency tank.

And then there were two, I just removed my Dalmation platy because she was lethargic, with stringy poop and all of her spots have dissipeard over night! They were there when I went to bed at midnight, now they are gone. She is in the medicated tank now, Im watching the last two adults like a hawk. If they are acting the same way when I get home then into QT they go. I can't tell if any of the babies have it or not.

I guess its down to survival of the fittest.

Im sorry you are losing them. Columnaris is deadly and you need to use the strongest meds you can. Any you first spot the signs of in the main tank remove to somewhere else.
If you are unfortunate to lose them all then you will need to strip the tank down and disinfect it including any nets and buckets etc. I would advise to get new gravel and filter media as well.