Ok good...since they are responding to the Furan, then it is bacterial we are dealing with. Keep up the water changes and salt in the tank along with the Furan....continue the Furan treatment for a full 14 days...even if they get better because if you cut the treatment short, the bacteria might get stronger again and they will develop a resistance to the Furan. So, carry the treatment out for a full 14 days and they should be fine.
-Ryan
-Ryan