The stronger/weaker split compares your rating to the average rating of your opponents, and by default it runs over every match including mixed. In 8.0 mixed you are partnering a 3.5 and facing a pair averaging around 4.0, so that average sits below you by arithmetic rather than because the competition was weaker. There is a checkbox on your page, "Only matches that count toward my USTA rating", and ticking it should give you a truer read.
Mixed does not generate an adult NTRP rating unless mixed is all you play, USTA Reg. 1.04F(1)d, and my engine gives it zero weight to match. So if nearly all your matches are 8.0 mixed, almost none of them are moving your number. What you are seeing comes from the few that do count plus your last published rating. I keep it in there and generate expectations in the match just so you know how you do. Even if you enter a friendly match by hand it'll tell you what your expected result should have been.
The one thing that kind of bites at 4.5. The higher you go the fewer people there are at your level, so more of your matches are against players below you, and the further above them you are the more you are expected to win by just to hold station. Beating a weaker field 6-3 6-3 might not be a neutral result, it could slightly be below par. That is the mechanic rather than a quirk of mine, and it means your rating should track the competition you actually face.
I had that calibration wrong until recently and 4.5 was the level it hurt most, sitting about half a level low.
@Jack the Hack turned me onto it. That is fixed and 4.5 now sits where it should be. So if it still looks wrong to you once you have the counting-only view on, send it through the feedback button and I will chase your specific case.
And the individual match ratings you asked about are in, so you can see what each performance was worth on its own. That was your suggestion so thanks!
