You will need to treat the main tank to treat the ich. Just placing the fish that you can see that are infected isn't the answer. If caught early the lifecycle of Ich normally runs between 7-10 days. If caught between stages it can be drawn out to 21 days. Ich also has three stages in its lifecycle. The first stage is where you s the "salt" looking grains on the fish. After a few days these cysts will fall off the fish and onto the substrate, plants-everywhere. This is the second stage. After a few more days the third stage begins as these cysts burst releasing the free swimming parasite. The parasite must find a host fish within 48 hours or it will die. This is also when ich is vunerable to treatment.
Yeah, it's normal for it to get worse before it gets better. As Menagerie mentioned, heat and aquarium salt will kill ich. Raise the temp to anywhere between 82-86F and and dose the aquarium salt at 1tbsp per 5 gallons. Treat for 14 days. After the seventh day, do two large water changes 12 hours apart and redose the salt.