Your boys are essentially teenagers experiencing their sex-drive for the first time - everything riles them up, every chance to display dominance will be taken, they're going to be nightmares this year and possibly also the coming spring/ their first "mating season". They'll eventually get over that hurdle though, and should mellow out (at least a bit). Even the sweetest of dogs have breaking points where they just dont want to put up with any more crap, and they dont always realize how big/strong they are. She may have hurt them unintentionally or something else could have gotten them or they might have hurt each other. I'd not leave them with the dog unattended for a little while more just to be safe (and to give her a break - just because she's not ripping their heads off doesnt mean she *likes* what they're doing to her. Best not to over-extend her patience)
If they're getting a bit too pushy with each other in the pool you could fence off a small area around it (doesnt have to be anything super secure or fancy, some garden stakes and chickenwire is fine) so that each one can have a little alone time in it without being fully separated from the other (so they dont freak out). Once they've each had their turn either take the pool away for the rest of the day, or take away the barricade and let them have it out with each other if thats what they choose (if they've already had a good swim they might opt to stay out of the pool if getting back in means confrontation)