Make sure there are no gaps between the sweep and the weatherstripping on both sides.
Use the proper screws and a hanger that can support the weight.
A patch can make the prized surface look like new.
Change your plants, use pots or waterproof the inside of the boxes.
Hiring a company to grind and hone the tile can get rid of “lippage.”
Carefully use a cleaner with alcohol, then follow up with a conditioner.
Fix it yourself with epoxy, or call a professional, who might be able to match the color better.
Stay away from acidic cleaners, which are likely to damage the stone.
And: how to replace the guide coverings on old windows.