If you have a hakko desoldering gun. You can use this to recoat those pads quickly. Run the pump while gently moving the tip across. Make sure to clean the flux off with naptha. Otherwise if you are quick with an iron and damp rag, you can wipe off the excess solder while still hot which leaves a nice smooth fresh coat. Again still need to clean flux off. The 2nd technique takes some practice. You can refinish card edge connectors in the same ways.

If you have trouble with the solder because of corrosion, a light rough up with a wire brush or sand paper can help get soldering started.