You've gotten some good advice, but I just wanted to say that I hope all is well with Minnie. I know Lexi has some "off" days, where she'll do more sleeping and seem to have less energy than usual. But then the next day, she is back to "normal". I think that normal is having different days, just like people. But your Minnie is too new to know exactly what normal is!
Welcome to YT and the world of Yorkies!