Limp, how? As in, she isn't tensing it/holding the muscle tone? If it's flopping around like it's broken, that is a whole different matter, though. Also, chubby, doesn't mean MBD. I have quite a few chubs here that are 110% healthy. Post pictures, though, if you're concerned.
Its definitely not broken, because when she eats she sticks it up in the air. Ill hav pics up tomorow and also weigh her and see what you think. does that girl in ur pic have MBD?