Dramatic change on "Visits by days since last visit" number since March 2015


#1

I have 3 websites on track with one Piwik server. I just found that since the end of March 2015, all of them have dramatic change on “Visits by days since last visit” number. “Visits by more than 1 day since last visit” dropped a lot. Is there anyone have the same phenomenon?
Is there any big change on Piwik update, Browsers, AD blockers or cookie policy happened at that time?

Metrics for Visits by days since last visit: 0 day

Metrics for Visits by days since last visit: 1 day

Metrics for Visits by days since last visit: 2 day

Metrics for Visits by days since last visit: 3 day