If any fish are flicking, they are infected whether you see spots or not, one of the most common areas for ich to attach is the gill membrane, which is not visible, unless you remove the fish from the tank, and look directly at the gills.
This is why any new fish, or feeders should be quarantined, and observed for at least a few weeks, before adding to the main tank.
Rid ich is a good treatment, especially where scale less fish are concerned.
With those fish, I assume your tank is in the 1000 gal range, so you will need quite the dose, and the may need to be treated a number of doses. I usually dose the tank every day for 3 days, take a day off, and start over. And vacuum thoroughly before adding each dose, to remove any dormant cysts.
I just treated a 500 gal system, and use @16 oz of Nox Ich and about 20lbs of salt.