Instructions to self to follow if you need to use the second YUBIKEY. THis is required till https://dev.gnupg.org/T2291 is resolved
sudo killall -9 ssh-agent gpg-agent
cd .gnupg/private-keys-v1.d
rm A7E4CAC527963BB0603F6E853738D2B50DCDCE91.key
rm C996662E616AD37885CF87BC1EE05AA1B0766081.key
rm DE6B3E9E1A3FCE768E6837A62E9F9A0B55ECA262.key
Alternatively, see https://github.com/rjekker/gpg-switch-card/blob/master/gpg-switch-card.sh
Also explained on the guide I followed: https://github.com/drduh/YubiKey-Guide#multiple-keys