My pom puppy's poop is weird. Help please!!?

I just got two 3-month pomeranians a couple of weeks ago. A boy (Sammy) and a girl (Winnie). Winnie is perfectly fine and everything. But Sammy tends to eat a lot more than Winnie and poops more. His poop is often jello-looking and has a little blood in it. I know the food they've been eating isn't different. They're eating Purina puppy chow. Do you think it's something with his stomach. Like do I need to take him to the vet?