Possible Velvet disease...help

[Sausage]

This is my first time on this forum so hello all

Right, so my orange molly which i purchased 1 week ago started acting strange 3 nights ago - she was swimming in the bottom corner of tank- which i have just learned could possibly be shimmying.
I went to my local pet store, had my water tested - which was perfect - i looked in the tank which i got my molly from the week before and the other fish were covered in fungus (white) and 2 of them dead.
My molly had been flicking off some plants a few times so the pet shop told me to treat with ANTI SLIME AND VELVET (INTERPET MAKE) which i did on tuesday night.
On wednesday mornign i noticed that i had some fry, i think may have came from my swordtail, not to sure.
Its now thursday and my molly doesnt seem better at all.
And i am now seeing changes in the other fish in my tank, my danio and swordtail also seem to be flicking on the gravel and plants and another of my swordtails seems to have a few red marks on his top fin.
Im so stuck so any advice would help me.
I dont want to loose all my fish and fry (the few i have managed to catch and put in a breeder with my 4 week old platy).
Thank you

 

[dkpate]

What exactly are your water parameters? How long has your tank been running? How often do you do water changes, and how much?
To check for velvet, you can shine a flashlight down the fish with the lights off, and it actually looks like orange velvet.
If it was my tank, I would get Melafix and Pimafix. Did you take the carbon out of the filter?