1.001 final gravity, consistently

So for the past 3 beers that I've brewed, I have gotten a final gravity of just about 1.000-1.002. I've been using safale-04. I did a blonde ale with a gravity of 1.052, a pale with a gravity of 1.054, and an oktoberfest with a gravity of 1.064. The only issue I've been having is keeping the temperature down. All three fermented at 78-80 degrees. I know this is way too high, but they all turned out well. Now that it is colder I can get that temp under control. But is that really the reason they are finishing so low? I've never had a beer finish under 1.010 before and now I'm getting them down to 0? I did check my hyrdrometer to make sure it works and water at 60 degrees is 1.000. Any thoughts and what is going on?

What temp are you mashing at and how accurate is your thermometer?

I've been mashing on the higher side, around 155. My thermometer is a candy thermometer from my HBS. It seems quite accurate as it shows 212 when water boils. If I'm mashing high, wouldn't I have more unfermentable sugars leading toward a higher FG?

High mash temp should give lower attenuation, IF the thermometer is accurate. Any off-flavors or bottle bombs? (possible infection)

I would suspect infection/wild yeast. Mashing at 155F should not produce a wort fermentable enough for S-04 to get down that low.

No off flavors, I keg so no bottle bombs. In fact the beer has been delicious. I just don't get it. It goes against everything I learned.

Does it taste that thin? A beer with that FG would definitely feel really light.

Not too bad actually. The blonde I did came out amazing, light, crisp and clear. The pale got better with age, but I could definitely taste a small off-flavor from the high fermenting temp. Neither tasted thin though.

A FG difference from an average ~1.012 to 1.001 should be pretty noticeable. If you think they don't taste too thin, I would consider trying a different hydrometer or something.

Your hydrometer or your thermometer are inaccurate, probably. You really have to strain to get a beer to attenuate down that far. The lowest FG I ever hit was 1.003, on a tripel with over 2 lbs of sugar. It just won't happen at normal mash and fermentation temps.