
Beta ProPlan went straight through my pups when I tried it, so even a 'quality' food is no good if it doesn't suit your dog.
If you choose to change the dry feed, be sure to make it very gradual, rather than run into more problems. You may find, as someone has already suggested, that feeding little and often makes a difference. I've never heard of a 9 week pup that was already on 3 meals a day. Changing to 4 may be all that is needed.
As for adding chicken, fish etc I too like to give my dogs something with the dry feed. Just be sure to introduce gradually, a small amount to start with, and you will encounter less problems. I would try to get the sloppy poos sorted before introducing loads of different stuff though.
Congrats on your new pup!