Ich is in the tank, which means it could be on all the fish whether or not you see it. Normally it first attacks the gills, which is why you don't see spots. If the fish do any flashing in the gill/head region, it is probably because the ich is in the gills.
There is absolutely no benefit to removing infected fish from an aquarium when ich is the disease. While you could be lucky enough to not have the other fish affected, the stress of trying to net a fish will certainly increase that fish's problem, and probably cause the other fish to become stressed. It is my opinion that ich only attacks stressed fish, and given time I could find you many knowledgeable aquarists who agree with this.
Remedies: I use Aquari-Sol when ich is severe enough to justify medications. This is a copper-based medication, as most ich remedies are, but it has significantly less of a detrimental effect on sensitive fish than any others I have used. And it is far less detrimental than salt on such fish. Corydoras and all the characins (tetras, pencilfish, hatchets) and fish like the delicate gourami species are highly sensitive to chemicals, salt and medications. I have used Aquari-Sol in planted tanks with more than a hundred fish and not lost one.
Prevention: Regular aquarium maintenance (weekly partial water changes of 50%) combined with minimal stress in the aquarium can prevent ich even when introduced on a new fish. I speak from experience. If the fish in the aquarium are healthy and not under stress, their immune systems will usually fight this off. Stress is caused by water quality issues, the wrong mix of fish (behaviours, compatibility), inappropriate water parameters, and so forth. Avoiding this will significantly reduce the chance of ich.