Red blood and dark stool?

Hello, my dog (a 2 year old Shih Tzu-Yorkie) pooped in a couple places last night in our bedroom. The stool was dark brown with diarreah like consistency. Also, there were some bright red blood spotting near the feces and bright red blood around her anus. I have her a bath and have cleaned it. For a little background, she is fully vaccinated and seems to be healthy and playful. We recently just switched her food from Blue Buffalo to Orijen Fish Blend. Over the last couple days, I am not sure if I have blended her food that well so I am wondering if this is the cause. I had a new bag of Orijen which I mixed in a tupperware with the rest of Blue brand....it probably wasnt a 50/50 blend so I am hoping this is why, but nervous it could be something worse. She also had some bile like vomit but does not appear to be lethargic and I am pretty sure she would eat a treat or her food if I fed her right now. Any help however would be greatly appreciated. -andre