Open new safari tab with a specific google account (gmail, gdrive etc.)

I have multiple google accounts, let's say they're called A, B and C.

A is my main one and, until recently, when I clicked my bookmarked Gmail page, it opened my "A" account.

If I want to see gmail for B or C, I go to the top right where the account symbol is, and switch to B or C.

Lately whenever I click the bookmarked Gmail page, it always opens it in my B account, so I have to switch every time to A, the one I use most frequently. I am logged in to all of them, A, B and C but for some reason now B seems the mail one.

What am I doing wrong? is there something I don't understand?