In the CompleteFTP Manager, under
SFTP Settings>Advanced SFTP Settings>Algorithms>Available Key Exchange Methods
click in the box and deselect 'Diffie-Hellman-Group1-sha1' (key exchange).
Under
SFTP Settings>Advanced SFTP Settings>Algorithms>Available Ciphers,
click in the box and deselect 'Blowfish-cbc' (cipher).
Both of these settings sometimes show up when a vulnerability scan is run, and are shown by some scans as 'deprecated'.