Child's speech was understandable, but now no one can understand her.

by Carla
(Austin)

My granddaughter turned 3 in October. She spoke right on schedule, if not a little early for her age. Babbled, single words, and then sentences. Clear and understandable to everyone she spoke to. In the last month, she her speech has become completely muddled. No one can understand her, not even her parents. If we can pick up on a word here or there and it's in context, we can figure out what she wants. Her mom (my sweet DIL) thinks it's just because my GD has a stuffy nose and that it'll improve. I watched her try to form words recently and its as though her tongue and mouth don't want to work in concert with one another anymore.
Her health is otherwise fine. She's happy and talks a mile a minute about everything, but no one can understand her.
I cannot find anything online about a child that could once be clearly understood, suddenly become impossible to understand.
I look forward to hearing your thoughts.
Thank you!