Switching to offset and resetting the parameters there is the answer but offset mode only affects parameters. If you start moving clips etc that is a global issue. ie. move a clip in offset and it will be moved in envelope mode as well (thankfully - wouldn't the alternative be er... fun

)
Offset will only offset whole envelopes as well, not individual or only a few nodes. If just a few nodes have moved that has happened in envelope mode, undo is your friend there, or perhaps autosave if you have it turned on.