I'm so sorry about Charlie
I can tell you from my experience..when Sophie died London was depressed. And sadly she still shows signs of it. I don't think anything will help unless i get another female her size to play with. After her death she slept a lot, didn't eat as much, i had to make her. I made sure to walk her everyday, i take her to meetups, dog parks so she can socialize and that helps but temporarily, then when we get back home she would just be sad again. She was so used to having sophie to play with cause Teddy doesnt play with her like sophie did. Now i take her out a lot more and never leave her alone, i take her bike riding with me, upstate, everywhere and i guess that is helping some. But she has her moments when she looks really sad or looks around as if she expects to see sophie
The only thing that will help is time and make sure to keep yours busy with playdates.