Adding a 3rd.

Fortunately, it's not all that common for two (or more) women to have severely incompatible vaginal flora. I salute you for tolerating that for six months, because I could not. If it happens again, see your gyno and get tested (and probably treated) for bacterial vaginosis.

That said, boric acid vaginal suppositories are the shit. I've been using them for 20 years now, either as a daily or every other day course of treatment for two weeks a few times a year, once or twice after having more prolonged or vigorous than usual hand sex with an existing partner, and after a new partner. I make my own and recommend it as the cheapest option (Amazon has five hundred 00 capsules and enough boric acid to fill them for about the same price as 30 premade suppositories).

Guys might not know this, but I imagine it's more common than most know.

When two women play together or share a partner, fluids invariably get exchanged. There are times this can cause a bio health change which can cause uti or yeast infections.

I was wondering if any women had tips on managing/preventing this.
For the uninformed once you take and add a new female partner. There is no realistic way to never share fluids.

Our last poly relationship this appeared to be an never ending problem for over 6 months. When that 3rd left we no longer had a problem. It's been years but we have a potential unicorn to start seeing regularly. We would hate for a reoccurrence of what happen last time.