Karen, I would be surprised if Maggie hurt Elsa, and if what she is doing hurt her she would certainly let you know, I would step back and just keep an eye on them, if Maggie hurts her Elsa will tell her and if Elsa gets too rough Maggie will tell her, they are tough little babies and although you do have to be careful if you had seen them play with each other you would of been shocked come the end, they would make a pile of 6 with one unlucky one underneath!!! They will have to teach each other boundaries and the only way they will do that is to try it out. Only once have I had an adult hurt a puppy and that wasn't one of mine but a lady who had three big dogs and 1 puppy, the big dog's were playing chase and the puppy ran in the way and got bowled over, that did cause damage but then accidents can happen and to be honest if my big dogs go silly the puppies are put out of the way, Maggie will naturally play nicely with her you know, she is such a nice natured girl. If Elsa is lying still under Maggies leg then they are also sorting pecking order out as well. Elsa is submitting sompletely to Maggie.
Tor Ludo did have a collar on up until the morning you collected him, I went in and it was gone!! One of his mates had taken it off and Andrew didn't notice when he cleaned up the room!!! So he should be fine when you pop one on him.