hi...try below.
1. move them to an individual clinical tank....100% new water and PP 1 to 1.2mgs and salt 100 to 200gm per 100L or water for day one..
2. day two 100% water change add metro 1.5gm plus 100 to 200gm of salt per 100L of water
3. day three 100% water change again and go back to NO.1..reason is there will some un-hatch bateria still remain inside..
4. repeat same as No. 2..for 3 days...that should solve the problem..