Could be a stain from the moisture / salts in your hand rubbing against it.
I have to say yes you are being too picky. You must have inadvertently put some substance or something on the computer which has caused the discoloration.
How does a cosmetic 'mark' on the bottom of the case affect the operation of the machine? Quite worrying.
I'd like to second this. As long as you don't scrub too hard you shouldn't cause any further damage, I've cleaned up a few MacBook's and MacBook Pro's with this method and it does actually work for a lot of stubborn stains and discolouration.Put a Magic Eraser sponge to it and maybe some alcohol, should come off. If not, you can try a warranty claim.
I'd like to second this. As long as you don't scrub too hard you shouldn't cause any further damage, I've cleaned up a few MacBook's and MacBook Pro's with this method and it does actually work for a lot of stubborn stains and discolouration.
I recently noticed this discolouration om my MacBook Pro Retina 15" mid 2014. Anyone else noticed somewthing like this? Will warranty cover this?It's only 3 months old and almost not used att all (3 charging cycles).
replaced the top cover at no cost.