Okay. There are a lot of things to address in the above posts that are speculation, bad science and hearsay. I hope to not sound like too much of an a$$, I just want to make sure we are all on the same page.
1) "Old hops"
I' m gonna say your hops were oxidized. ( not stored cold and/or in open air. This gives a " cheezey" note that is like Provalone or like foot odor. I say oxidized hops ... AKA ; cheesy hops
Here's the thing, it would take sitting & baking in direct sunlight or a year in a sealed Tupperware container for whole
hops to go cheesy and nasty. More time if pellet hops. How do I know? I do this on purpose for my lambics. I have nearly a pound of Tradition whole leaf hops that have been left at room temp in a sealed container for over a year and they've gotten a bit less green, some are yellow-ish, none are cheesy. I baked a half pound of US Goldings in my car over the summer - now those were cheesy! (Whole leaf again.)
I store my bulk pellet hops in the freezer in Ziploc baggies to no ill effects - sometimes for a year. The OP's storage methods are just fine for what he's doing.
2) "Too hot of a sparge"
BTW... 175 is too hot for sparge... Don't go over 168 or your asking for grainy notes.
The OP stated he mashed at 156 and did not mention a mash out, meaning that adding 175* water to the mix would result in 167* water (assuming 3.5 gallons strike and 5.5 gallons sparge). So there's that. BUT, even if he did do a mash out to 168* and then added 175* water, the resultant temp would only be 172* (which is the upper limit for a Hochkurz Mash
Also, "over-sparging" or sparging at too high of a temperature results in astringency (akin to chewing on grape skins - a prickling in the sides/back of the throat), not a grainy flavor.
All that being said, "dirty socks" is likely an issue with sanitation. Should you watch your sparge temps? Absolutely, but it is not the issue with the dirty socks.
Okay, peace, love & tranquility.