Here's an example of the wrong nails--
Black Bleeding streaks.
It gets worse. If this is pressure treated-ACQ Rated Materials and regular galvanized nails, the nails may be rotted to failure within 3 years. If it is red or white cedar, you will find that there is no method for removing these streaks. The iron reacts with the tannins chemically to create the discolouration.
There are special double galvanized fasteners specifically for use with ACQ Materials.
Nothing will help this fence if it is ACQ materials. Wait until it falls apart and rebuild with the proper fasteners.
If it is cedar, think about a solid stain or a very dark semi-transparent finish.