My dogs are playing aggressively with each other?

Hi, I've asked a million and one questions about dogs in the past few weeks, but dealing with dogs, there are always a million and one more questions to ask. Anyways, I have a GSD Lab mix puppy named Sam. He is 5 months old (in two days) and around 30 pounds. I recently added a 14 week old lab mix named Marley to my family. She is around 35-40 pounds (I think she is mixed with a mastiff or something LARGE like that). Anyways, they play aggressively with each other and I'm not sure how to get them to stop. Telling them firmly no and pulling them away from each other doesn't seem to be working very well. I also crate them after they get too wild. Marley's teeth are very sharp for her young age. I'm afraid that they are going to accidentally draw blood or injure each other. Can someone give me some tips before one of them gets hurt? Thanks. Please, don't leave any ignorant comments. I am doing this to make sure my dogs don't get hurt.