This puppy is still wet from being birthed . Always a good practice to take the weight and time born and put on a chart for each puppy twice a day.. if more than just a few you should add colored collars, so they are easier to extinguish. Once in the morning and once at night..Some pups or all pups may lose a few ounces in first couple days till moms milk starts to come in. First few days she will have colostrum , which is very beneficial to pups health. After a few days right away pups should start gaining weight. If you have a few that are not, them are the ones that could be in trouble.. sometimes in larger litters you may have to sub some with a bottle  with goats milk replacement for puppies. Always remember if doing Tails and dew claws , it is best done within first two days of life.