Pardon the paragraphs, but I think it's best to take a break and keep focus. I legit just had this happen to me, though slightly different situation. Got distracted by a new shiny project (which was inspired by a darn contest). My problem was I focused on it for a month and forgot to upload a few eps of my main series (which JUST got back from hiatus, lol) Honestly had this idea for a while, just was waiting for an "opportune moment" to do it, oops...and now I'm thinking it won't get published by the deadline, so why did I bother?
I get that one benefit of having a new project is the thrill of doing something new, and that can somewhat help get your motivation back, BUT you'll soon have another project to juggle against your other works, and that is horrible for productivity! If you had only one other story to do, then I'd vote "go for it", but you have 3 now, so I wouldn't advise it unless you are absolutely unmotivated/bored with your current batch of projects.
I'd suggest breaking away 100% from writing for a little bit, maybe jot down any new ideas or outline them if only to get them out of your head, but don't execute them yet. Keep your main 3 as your focus until they are finished. I think finishing versus starting is a better creative goal, but that's my honest opinion as an ADHDer.