That’s odd! My guess is he’s stressed and is showing his stress. I saw your other post about the kittens…is HE neutered? Do you have 4 litterboxes (one per cat plus one)? Are those litterboxes VERY clean?
Bringing in new animals cause upheaval in a home, even if you do it the right way with slow introductions. ASSUMING HE IS IN GOOD HEALTH, and assuming you’ve had him checked since this started, I’d suggest picking up some feliway from petsmart or petco. I’d also prevent him from going into the bathroom with you.
Eaten*
Not much you can do at this point! If she did eat one it may pass with no problems. You need to pay attention for the next few weeks for signs that it didn’t pass and is causing problems – such as her refusing to eat; eating and then vomiting within a hour or so; listlessness, etc.