% ssh ohstp
ssh_exchange_identification: Connection closed by remote host

I have 4 hosts in my $HOME/.ssh/known_hosts file. I used to be able to ssh to all 4 with no problems. Just recently I started having issues with 2 of them. I removed them from my known_hosts file hoping it would ask me if I wanted to add them, but it did not.

All I get when I try is the above error.

How do I get rid of this error and get these entries back in my known_hosts file so I can connect to the hosts?