Looks like I have four girls and two boys, at least as far as I can tell

Mom has ten teats, I guess that is normal, but four of her teats look flat and I don't think any milk is coming out or the pups can get latched onto them. Does anyone know if that is normal? That leaves six teats, one for each pup. I'm constantly checking to make sure every pup has a teat

Does anyone know if and how I can make the other four teats work? They sure would come in handy!