If watchtower is running, your docker node should now update automatically. However I would suggest you do the manual update procedure for your docker node asap. I suggest this because nodes that are more than 2 minor versions out of date will be disqualified if they aren’t updated quickly enough. It may already be too late for your node, but it is worth a try. Watchtower can take up to 72 hours to update your node. For future reference, the current version number is (almost) always the same across all platforms.
I suggest you do not update your docker software, as I know people have had issues with newer versions. The official advice is to run docker 2.1.0.5 .