Big mistake setting the posts in concrete. Concrete is essentially a big sponge. It gets wet, and never dries out. The only posts I ever set in concrete are gate posts, and that's only to keep the post from sagging.
Over 20 years ago I built a large privacy fence for a neighbor. All of the posts were set into pounded gravel. The only posts that were set in concrete were the gate posts. The only posts that rotted (yes, pressure treated wood rots, eventually, especially if it's kept in contact with constant wet) and had to be replaced were the gate posts.
Take the old posts off. Dig out as much of the old post out of the concrete as you can, more is better. Fill the cavity with a good high strength concrete, and drill a post foot onto what is now essentially the pad. The foot will keep the post off the concrete and will provide a good solid base.