The scores will go up, and then the scores will go down. Then they'll likely do more of those two things, without ceasing, for as long as they exist.
I don't think you should worry about it further. Scoring between 80 and 85 is quite good enough, and a hub scored that high could well get as high as 100, and then it may very well drop to 70.
It annoys me a bit when mine are below 80, but it happens. My opinion is if something is below 75, then it should maybe then be attended to.
The simple fact is the score isn't that big a deal. I do not know for certain how it goes just now, but at one point when a hub's score was 65 or below, it meant they de-indexed the thing. That isn't the case now, something can become unfeatured with a very high score.
Scores just aren't that important. They have some sort of significance, but what that significance is may well change.
Don't sweat petty stuff or pet sweaty stuff. Something like that.