What is your puppy nervous of?
You say pup is ok at home so it is probably a case of working on outside distractions.
It is quite normal for a puppy to be unsure of new noises/sights such as traffic, bicyles etc.. and these encounters should be included in your socialisation plan for your puppy.
I agree that a change of diet can make a real difference (without starting a food debate

) I changed my puppy from Beta to Arden Grange and the change in her behaviour was clearly noticable.
If there is a specific thing that causes fear in your puppy, maybe we could advise on how to work on that before considering remedies?
Having a 9 mth old springer I think it would take a few bottles of neat alcohol to calm her down entirely LOL, I'd worry more if she was over confident or fearful all of the time.