Yeah, I was surprised at how much it swings, but it's high enough it shouldn't matter (and easy enough to not use the cards for a month, let it rebound, then borrow whatever I need to borrow).
The report from my bank never says why. It does list factors that contribute to my score, but they're all "good" (low usage as % of available, all payments on time, etc). And never change.
I'm signed up for all the credit bureaus free accounts so I can freeze/unfreeze my credit. They send out reports monthly, along with one of my CCs. All of them have the reason. And yeah, the score is ~800 so it doesn't really matter. Still interesting to see how it moves with relatively small balance changes.
The report from my bank never says why. It does list factors that contribute to my score, but they're all "good" (low usage as % of available, all payments on time, etc). And never change.