It's highly likely if they aren't infected already, they will be soon. Just removing the 2 infected fish didn't remove the Ich from your tank. It's still there in the rock, sand, etc. Which is why it's necessary to go fallow (fishless) to starve it out. Ich will only die when it's robbed of a fish host to feed on. As for not seeing symptoms, Ich will sometimes live in the gills and not show itself under the skin - for months.