You also don't mention if you've installed extensions and how many. Although extensions to browsers can be useful, some can be resource hogs or incompatible with other operations. In my experience, both with my own browsers and those of friends/coworkers who ask me to look at similar issues, it's amazing how many extensions can get added and then forgotten when they don't prove as useful as originally thought. Although the extension isn't being used anymore, it may still be creating problems.

You may not have extensions added, but if you did with Chrome and Firefox (and eventually will with Edge), this is a problem I would consider.