I was by all of my cats sides when a few passed away this past year giving palliative care when they were so sick. I didn't give up on them until they were ready to go
you did the right thing... do you foster them or are they yours since kittens? 
A few were seniors..others..too young but had been with me for a few years. It's been a rough year but I will always take care of them even when it's hard for me- They deserve it.
really kind of you! 