I´d actually say start a new one. The exposure thing is right, and also, if you start the new volume in your old "post", people will go back to start at the first episode which might throw them off, then (not saying it will, since I have seen nothing of your Webtoon). 85 subs is indeed not a lot for a Webtoon Comic, and thoose faithfull readers will follow you to the next Volume anyways if you link it often enough 