Dying Trees?

Three of my trees (3 White Oaks and one Blue Spruce) are dying. The have white flowerlike fungus on their branches and are loosing their leaves (and needles on the Spruce) starting close to the trunk working it’s way out. I have bought a tree bug and fungus killer at Lowe’s to apply to them, but I am not sure if there’s a better way? I am desperate to save these trees.. Thank you.