Did you make sure that your Firefox isn't remembering the wrong login as if you set to save logins then you have to make sure you click the right login name to use for login. As to Chrome and how it manages the logins I know if you use multiple site login if you set to remember you have to click the right login to login to the site as well.

Suggestions in a login drop-down menu that have a key icon in front are login suggestions that you need to remove in the Password Manager.

• https://support.mozilla.org/en-US/kb/password-manager-remember-delete-edit-logins

Suggestions in a drop-down menu without a key symbol are autocomplete saved form data. Suggestions without a key icon are part of autocomplete saved form data that you should be able to remove by selecting this item with the cursor Down key and pressing Delete (Mac: Shift+Delete).

• https://support.mozilla.org/en-US/kb/control-whether-firefox-automatically-fills-forms