Can't win games in diamond IV

I was at D2 90lp yesterday and ever since my demotion from loss streak due to unstable internet yesterday I haven't been able to win any games in low diamond. I am in D4 now. I am not even complaining about bad luck etc. I just cannot win. I have average rolls/items and I'm not tilted/raged. I am very confused. So either I have to play a significantly different style in low diamond than in upper diamond or everyone all sudden became really good at this game in one day?