It would not surprise me if a single password is enough for an attacker to guess the rest in this scheme. It is common enough to be predictable, and even if it

It would not surprise me if a single password is enough for an attacker to guess the rest in this scheme. It is common enough to be predictable, and even if it weren't, all your passwords are at most 2 characters different from each other. That's not a lot of entropy.