I have a 14 week old puppy too and he is SOO picky! My vet told me he was a little underweight about 2 weeks ago since he's still not 2 pounds yet and that really worried me so I changed his food from Eucanuba to Chicken Soup for the Pet Lover's Soul dry puppy food....he LOVES it! It was such an instant change and it even cleared up the tears and gunk he would sometimes get in his eyes.
Also I don't think he would eat much because he gets so excited and follows me around everywhere (forgetting to go eat) so I found that using his kibble to teach him obedience skills like sit, laydown, etc. got him to eat a lot more. Not sure if this helps but I know it helped with mine! Just make sure to always have nutrical on you at all times just in case
Good luck!