[sweetlee]

The obvious is a bladder infection, ask for a test. The frequency would suggest that as would the drinking so much water. Also a puppy who pees just a drip would make me suspicious.
If you don't think your vet is being thorough enough, there is no law saying you must stay with that doctor.
I doubt the food is causing it, but you are right Nutro probably is not the best choice.
Too many grains and not enough meat.
If you search on food around here you will find the most popular choice is probably Canidae.
And of their formulas the most popular seems to be the ALS.
I have priced foods and looked over how much I would need to feed calorie wise and find that feeding the Canidae is actually cheaper than feeding Nutro or other midgrade foods because you can feed less. And value-wise it is probably the best buy. Not all dogs do great on it, but it seems most people are very happy with that choice.
Pricewise I believe it's about the same for a 40 lb bag but you get much more meat and alot more calories in one cup of Canidae.

Sharon