@6Foot7Dad,
This is unfortunately something of a Catch-22. The interference may be read as high as a result of your Decos currently communicating over your network, and the optimization feature cannot really distinguish between the two.
Also, since the Decos create a mesh network, there is no way to manually set the channel, as it is determined by the optimization feature.
If you are concerned about interference, and it is affecting your network performance, I would recommend looking for an app on your phone that will perform a scan of nearby channels. Using this, you can determine if it is your network, or if it is interference in your home.
As long as you are receiving your expected speeds and are not having issues, the Deco app will automatically manage the connection to provide the best experience; and unless you are in urban housing where people are stacked on top of each other, changing channels does not often provide any tangible difference in performance.