A few things to mention. Channel Catfish will sometimes eat at the lower temperatures but usually feeding is either stopped or drastically reduced at below 50 F. The temperature guide here is probably pretty close to what I do (http://www.suttlefish.com/raising_catfish.html). A sinking chow works better when the water is cool or cold. If all you have is a floating chow then soak it for 10 or 20 minutes and then give it a squeeze to remove the air and it should sink (some require a bit of extra effort). Sometimes fish will take live food or something like hardboiled egg that's been chopped up even when they won't eat the commercial chow. It may take some work getting them back on regular commercial feed but you can.
Catfish are a bit chicken when it's cold or cool they get a bit picky about eating or coming to the surface while you're watching. I've found that they'll eat food left overnight on the bottom of the tank - if they don't then remove it and wait a few days before trying again with some fresh food. If they eat the food then see if they want a little bit more the next day but don't over feed.
Yes it's OK to not feed them for many days and even weeks. Younger fish need to be fed more often than older ones but they're all pretty adaptable because they don't have to regulate body heat the same way we do. Going on vacation or dealing with fish disease issues may mean you'll need refrain from feeding for two or three weeks. In the winter like this I'd still try to feed them every so often. Just leave it in overnight and see what they do
