Intresting numbers when looking at the winrate of champions while they're on the free rotation

So I've been collecting stats on a champion's WinRate during the free rotation, and I've found that while most champions lose some WinRate during the rotation some champions actually have an increase in their WinRate. For example,

went up a total of .34% went up a total of .46% went up a total of .66%

These increases in WinRates usually are around .5% or less with a few going up to .75% increase. For comparison here's some of the champions that were also on the free rotation that week whose WinRate went down,

went down 2.35% went down 4%

That's around the average. These all can be explained with some outliers, not big enough sample size, or just simple sampling error, but what I've really found interesting is Janna's WinRate during this same rotation. Her WinRate each day except for the first was higher than the day before she went on the rotation with an ending ▲WinRate of up 1%. This is a higher ▲WinRate change than any other champion on the rotation by .25%. I feel like sampleing error can't explain that big of an increase. Also her Playrate skyrocketed on day three from 8.48% to 22.56%. Effects of that jump were still being seen untill the end of the free rotation. None of the other champions saw a pattern like this. I was just wondering if anyone here knows of any explanation for Janna's sudden spike in WinRate / PlayRate on that day? (Free rotation cycle I'm talking about is the one from Oct. 4th to Oct. 11th)