Why is my 13 week old bulldog puppy having diaherra in her crate?

My 13 week old bulldog has been doing great crate training. We hav3 had her for 4 weeks now. She has recently just started having diaherra in her crate and having no problem laying in it. What is the issue? We take her out before bed and then get up with her 4 hours later to take her out. She just recently started pooping in her crate, literally the last 3 nights. Help please. Thanks