WordPress Admin login issue

i am facing a strange issue, i have around 450+ WordPress sites, hosted across multiple providers (some on shared hostingS, some on VPSs, around 8-9 different locations & providers) But since last night, wordpress amdin login stopped working for almost 90% of the sites.

It says wrong password, (i am 100% sure i am using correct password). These sites are not related / connected to one another anyway. & most of the sites are having exactly same issue.

Sometime (with some sites) if i am able to login it redirected to the link like below

http://www.mywebsite.com/wp-admin/

Except the problem one thing is common between all sites, i am managing all these sites with https://managewp.com/

What can be the issue? or possible solution