You can always change your HTTP Auth credentials, from your Opensolr Index Control Panel, by clicking on the Security tab, on the left side of the index administration menu.
IMPORTANT!
When generating a new API KEY from your Control Panel Dashboard, that will NOT also change that as the password of your EXISTING indexes.
Only the NEWLY CREATED indexes, will adopt the new API KEY, as the password.
The existing indexes will continue to use the OLD API KEY from the time before you generated a new one.