Well...there's your problem! Repeat after me: "It's not people food." Ok sorry, couldn't keep my smart-rear-ended comment to myself.I was eating Purina Puppy Chow.
If you switched on sunday then you need to give it more time. Since you started at 50:50 keep going on that for a while, then 25(old food):75(new food) for a bit more, then you can transition him to 100% new stuff. Pumpkin is a good "binder" and the yogurt will replace the good bacteria in his gut while his intestines clear out the garbage. If you know anywhere near you that sells The Honest Kitchen supplements, they make one called "Perfect Form" and it's an additive to help your dog transition between foods. Also, be careful on the amount you feed him. I'm not positive, but I'd imagine with a higher end food like Fromms you will need to feed much less than with the Purina. Too much of a good thing will also cause intestinal distress.