A safe bet would be to do a full spectrum treatment. That means antibiotics, antiparasitics, and salt. I use API E.M. Erythromycin for bacterial infections, API general cure for parasites, and Kosher Salt as my aquarium salt.
can't tell from the pictures but I would do a 75% water change and gravel clean the substrate every day for 2 weeks. And I would add 2 heaped tablespoons of rock salt for every 20 litres of water. Keep the salt in there for 2 weeks.