I have seven of them in my yard and every year some of them start turning brown. Some years they will be fine but then turn brown the next. I don't ussually fertilize them and water routinely. My ferns are about 3 - 4' high and are native in my area on the northern CA coast. Anyone have a suggestion for what I could try? The second photo is of the ones that look good. TIA.

EDIT: I should have included one of them that isn't looking so good. This one was planted the same time as the others but gets morning sun, the others get afternoon sun: