I would use them, I am thinking they should last 3 more season maybe more.
I am (guessing) thinking that some dissimilar metal is causing this. The circle? machining marks? I am guess you have zincs on the prop.
I would think more damage to the edges if electrolysis , Maybe copper paint on them? machining added different metal to the blade.
Not sure if I would coat them with anything, still thinking about that.