Please share your experience..

I have a 1 year old pup. Last 2 days changed his food from biscuits and wet food to just wet food. (Done it all correctly) last 2 days his been so weird bringing his bowl to me every 2 minutes begging for more food. Sitting on the other side of the room next to his bowel, pretty sleeping. One min solid black poop then runny poop sorry tmi! Just not himself? Is it because I changed food? And it may not be as fulfilling? That he is just having a growth spert?