Hello Krissy2u and Welcome to Fish Lore!
Sorry to hear that you're dealing with
ICH. If one fish in the tank is infected then the entire tank is infected and has to be treated.
What is most recommended is:
Raise the temperature in the tank to 85 or 86 degrees. Leave it there for a period of two weeks. The high temperatures interrupt the ICH life cycle and it dies off. Please note that ICH may appear worse before it gets better. Do 2 gravel vacuums each week to remove the spores that fall off the fish and into the substrate. Warmer waters require more oxygen so an additional air supply line/air stone should be added if you aren't currently using one.
I only recommend using medications to treat ICH as a last resort. I think the fry would have a better chance of surviving the increased temperature compared to using medications. (my opinion). Too, some medications can ruin your cycle so you really have to be careful here.
Best wishes!
Ken