The problem of spam is almost impossible to solve with only plugins alone. You  should combine different methods, including software on your server. e.g fail2ban, spamassassin, iptables etc.

Are you making full use of the Spam Login Filter plugin, i.e. have you created an account at https://www.stopforumspam.com/ and created an API key and do you report the spammers when deleting their accounts from your site? Doing that is mandatory to reduce the creation of spam accounts because it adds their account credentials to the Spammer blacklist that is checked by the Spam Login Filter plugin on account creation. So, by reporting the spammers you reduce their chances to return. It might not stop them completely (and also might not show an effect immediately) but it should help to at least reduce the creation of spam accounts after some time.

Other than that you can only try to figure out if the spam accounts show any patterns in usage of email domains of IP addresses that you might be able to block completely (by domain or country of IP addresses) without losing valid members.

Yes Iionly, I have the plugin synchronized with StopForumSpam and I try to report those users that I think are spam. The plugin itself has a section to include possible spammers.

I must confess that the flow of daily spammers has dropped, perhaps it was a specific failure in the StopForumSpam service. Thank you!

i would suggest to close or turn off the new user register service and leave a note or blog to say if you would like to be come a member is email you or the admin team, and you make the new user account manually, i know a little more work but it will stop the spam of accounts