I'd remove any inverts you can and lower the salinity in the main tank to about 1.017 or so over a day or so - sounds like a nasty outbreak. Additionally raising the temperature some will speed up the life cycle of the parasite - if they are in the 'spot' stage you may be able to get them to drop off and take other measures before they reattach to the fish.
Possible a ph flux added to the sudden temperature surge could have stressed the fish enough to allow the parasite to infect them - some people believe you can totally eradicate ich, others believe it can exist at a subacute stage indefinitely waiting to explode on stressed fish.
Good luck.
30 Gallon reef, 220 gallon South American Cichlid tank.