The gap between kanji and furigana changed for me within the past 2 weeks. I've noticed it in quizzes on the answer page for vocab, but it's more of a problem in shiritori because the definition gets cut off. Firefox on Android.
I can't seem to attach my screenshot here... Another bug. I will add it on desktop later...
It's firefox :( - there has been absolutely no change to any styling code on renshuu, but firefox has always done weird things to the spacing on the furigana text. So it's quite possible that something in their app has changed.