If you bought some new fish, then this is where quarantining comes into place. Did you quarantine your new fish? To be more precise, do you ever quarantine every new fish at all? Regardless of the sources, we need to quarantine every new fish to avoid further health problems with our older stocks. There are plenty of parasites that are often overlooked, whether the source is reputable or not. I would advise quarantining for 3-4 weeks. The longer, the better as most parasites have a longer lifecycle and may make it difficult for you to eliminate them in the end.
There are many parasites that can be associated with the scratching symptoms. It is not only ich that causes this unusual behavior when done frequently. Flukes, nematodes, external parasites and flagellates are also responsible for that. If at all possible, get praziquantel and treat your fish for possible flukes. Praziquantel is a mild treatment and does not harm the beneficial bacteria so you can give this a shot to destroy the possible flukes.