Excessive Pooping

My 6 year old schnauzer has starting pooping a lot more than normal. I let her out before bed (around 11-11:30pm) and she usually poops then, and can usually make it all night, until I get up @ 6am, she goes out again and may or may not poop. She can usually hold it all day while I am at work, now she is having to go again in the middle of the night and again during the day. I haven't changed her dog food or treats. Any assistance?