C.S.
Growing up, touching or discussing the genitals was always forbidden. I may as well assumed there was nothing there.
My older daughter was never a toucher, but my 4 year old found everything long ago and has no shame.
When she is tired, she puts her hand right up her shirt and rubs her boob until she falls asleep. We tell her to get her hand out of her shirt and she laughs and sticks it right back up there as soon as we walk away. I mentioned to the doctor and she smiled and said, "it feels good". As well, she said you just have to teach them they do that in private and not in public.
I wouldn't worry unless there is a rash or fear of an individual when the diaper is coming off.
It is hard to live with other families, but you do have to have a certain amount of trust, or you shouldn't be there.