While Betadine is an excelent topical antiseptic for wounds etc. I would not recomend it in this case do to the close proximity to the gill, eyes and mouth.
You can use (in your tank with a high PH and harness) a combination of Triple sulfa and Malachite Green at half dosage.
The use of Triple Sulfa with Malachite Green can buffer the effects of Malachite Green in fish such as Clown Loaches, Catfish and other sensative fish. The use of Triple Sulfa with Malachite Green also provides the benefit of increased secondary infection protection, especially effective against Fungus (Saprolegnia) & Columnaris.
Do a 50% water change and dose half the recomended dosage. As always make sure any carbon is removed for the filter. If the fish shows any signs of not toleration the treatment discontinue and do a 50% water change two days on a row to remove meds and/or replace carbon. The fish should tolerate this since your Ph is high with hard water. MG is harsher in soft water with a lower PH, so this is a very effective treatment with your water conditions. MG & 3x sulfa ia also much eaiser on your BB than some other treatments.