You are SOOL. I mean, you can ask nicely for changes but that is about it.
I share 50-50 custody with my ex. My elderly parents live in a basement apartment attached to my house, so we've been very careful about social distancing. My ex is pretty good at his house, but he allows his girlfriend's (affair partner during our marriage) 3 kids my kids regularly, and I have no idea how careful she is with her kids or how careful her ex is with them on his time. I also saw her the other day canoodling in the park with a man who was most certainly not my ex husband, so goodness only knows what my kids are exposed to via her.
But.... not much I can do about it except control our environment here and teach my kids good hygiene habits.