I'm so sorry to hear that. Just know that you're not alone when it comes to knowing how much it can grieve us to lose a beloved pet...one of God's creatures that does so much more for us than we do for them...their unconditional love, their ability to see past our shortcomings and love us anyway.
“My goal in life is to be the kind of person my dog thinks I am.”
Sorry for your loss. As hard as it can be to accept, you made the right decision. It's not fair to let them suffer because we don't want to let them go.
The method is not for everyone (and sometimes simply not possible), I have read that letting the other dogs/cats see & sniff their recently passed sibling for a brief period is most often helpful for them understand they've passed.