ok - flat out, you need to address this (for all of you that are having problems) like your dog is brand new.
the dog should not be allowed out of your site. the dog is attached to you, and you are supervising it all the time. if it is not attached to you (via leash), then its crated. the dog is not allowed to run around, is not allowed to do things when you arent there. you watch the dog and you walk it at LEAST every hour, reward heavily when it goes outside. you interrupt it if it goes in the house. you walk it after playing, aftering eating, after sleeping. the dog needs to understand that the ONLY acceptable place is to go outside - right now, i just dont think its really sticking with them - they know you CAN go to the bathroom outside, but theyve gone too much inside and perhaps been given too much freedom, too soon.
yes, the dog needs to learn that it needs to let you know when it needs to go out. right now, it decides when it goes in or out. it makes all he decisions regarding the bathroom habits - so why shouldnt it just go where it feels like. they are young, and need supervision. they need to be reminded that they need to go (how many times when you were a kid did you hold it until it was almost too late?). they need to be reminded WHERE to go. they dont get to make decisions for themselves. and then they let you know they DO need to go, they get rewarded heavily.
i would simply take it back to step one. my mother use to say she could pretty much housebreak a puppy in 24 hours by STAYING with that puppy at all times for 24 hours and walking it very frequently. if the dog doesnt know going to the bathroom in the house is an option, then it wont do it. if going outside is the norm and the only thing it knows, theres no confusion.