Lost one of my dogs
My most sincere condolences. As a multi-dog owner who has dealt with this more than a dozen times, I know that nothing any of us here can say will help alleviate the pain you must be feeling, but perhaps rest easy in the knowledge that Noah lived his Best Life with you, as 15 years for a 105 pound dog is quite exceptional. He was certainly well loved, and loved you back in his own way, I'm sure.
Give your remaining two pups some extra special hugs and kisses, as most likely they are feeling the grief as well.
Our hearts go out to you.
Jim, Julie, Claire, and Belle.