Whats up with my Spark plug discoloration? (Picture inside)

My car is a 2002 mustang GT 70,000 miles all stock. (not my old car in sig)
My car has been idling a little rough and feels like there is a little miss at part throttle. It is a all stock car except catback and k&n drop in filter. It is also a weekend warrior and meticulously maintained in show room condition. Has a fresh tank of 93 octane in it. I put these plugs in just for regular maintenence about a year ago and they have about 300 miles on them. These are just 3 random plugs i pulled and havent pulled the rest. The one on the very far left is cylinder 8 i beleive ( driver side far back) and the rest are from the same side. Never saw plugs before that looked rusty colored. The other two are rusty color in spots and the tips as you can see are a silver color. Havent installed a new fuel filter yet? what do you guys think and have you seen plugs like this? The old plugs were a nice sooty dark brownish color like you would see typically of a healthy engine. Im thinking whatever the reason for the plugs being like this is the reason for the recent rough idle and miss.


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oh ok. the rust color must be from the octane booster i put in the car before the winter along with the fuel stabilizer. How about the silver colored plugs, is this lack of fuel i presume?

ok thanks bud. ill just run some fuel system cleaner through it anyway

thanks man. I had that thing for sale for a few weeks on here about a year and a half ago but wound up sellin it on ebay for 10500. Took a big loss but thats part of the game i suppose