Re: border collie puppies
You did the right thing by making the fence lighter.
There is a line that goes across the top of the dog's head (on the right) that lines up with the top of the fence. Often it is best to make lines stop at a T, rather than lining up with other objects. I was going to suggest you move the fence up or down a bit, then you could keep it dark.
I think a stronger source of light would help define the forms better, with the dogs, the girls face and hands too. You paint well, so I figured you knew that already but it was not clear from your underpainting.