sorry, don't have any experience of Bassets. Can your breeder not give you some advice? If not, go here for a list of Basset clubs & contact one of them for info.
Hi I would try puppy food for a large type puppy, basset hounds are a large breed on short stubby legs and maybe your puppy is not getting enough nutrients for his size. A male will be anything from 60lbs to 80lbs full grown and a female 55lbs 65lbs. I used to give my pup a meal of readybrek for his breakfast every day ( and still do ) he's now 16months old and weighing in at 3 1/2 stone and still growing. One good thing about basset hounds is they will eat anything they just love their food. I hope this helps you Carol and Dexter ( basset hound ) Ps as for drinking a lot they will do this when their food is a dry bisc type they need water at all times.