So I have had these slp headers for maybe 3 or 4 years. Is this typical for them to rust? It seems to be only on the one tube coming out of the front far left cylinder if you are looking at it from the front of the car. Any thoughts??

They are mild steel. If any of the coating comes off, it will rust and spread.
I guess the quality of the coating or how it was applied just wasn't that good.