You are most welcome!
Well, the good news is your mousey kids sound like they are doing just fine if they are playing, grooming, eating and do not seem lethargic or listless and you do not see any physical symptoms that would indicate they are sick, and you see them drinking from their little caps of water that you mentioned, so I am stumped as to why they suddenly decided they do not want to drink from the water bottle!
You are correct, a water bottle is the best and most hygenic way for lil critters to get their water, since pots or bowls of water can get easily soiled or have bedding kicked into it. Not a clean way for your babies to get water, agreed, but I know you want to make sure they are getting their very important 24 hour access to fresh water, as all animals need, so wow, I am just not sure what to make of it!
My husband, who prides himself on being Ratty Super Dad, listened to me read your post to him and his first thought was, "I bet her mice ARE drinking from the bottle, but she has just not actually been in the room when they do drink," but you said the water level is not going down, so hmmm!!
Well, I am not sure what to suggest at this point. Can you try some more tap taps with your finger on the sipper tube to remind them that, "Hey, there is water in here you guys! Try it again!"
(I am sure they did not just suddenly "forget" how to use the water bottle, but I am grasping at straws here to figure out an answer to this puzzling predicament!)
P.S. You have not been adding any of those store bought vitamin drops or anything to their water bottle water have you? I was just wondering because I know that those vitamin drops they sell to put in your little ones' water bottle can make the water taste funny and the mice (or rats!) will stop drinking from the bottle if it tastes funny)