New fin growth generally will look-clear to white when it first start to re-grow and it will usually start to color up with time, however, depending on the damage itself, nutrition and a few other factors-sometime the new growth may or may not return to the color it was to start ...with really bad damage often the fin never return to their full glory...it can vary a lot and it can take weeks to month for full re-growth...but white/clear edges is a good sign....great that he is eating good...
I exactly follow your treatment plan. I use thermometer so the temperature of water change is exactly the same as his quarantine water. His caudal fin is growing but I don't know if this is a new fin growth. I tried to find on line pictures how new growth look like, but I wasn't successful. From descriptions I found that it should be clear, transparent, fragile, thin like cellophane growth and our betta has like thick, gel growth. His dorsal fin started change color from white to more redder, natural color.
He is eating very well and is very active
When I premix my treatment water-I generally use it for the duration of the treatment and only mix more as I need it-the longer the tannin source steeps the more tannins are released-the darker the water and this is what I want....Be sure to shake well before use and check the water temp between the two so not to shock the fish with extreme temp changes.
I would like to ask you question about treatment water. Our betta is in his 6 day salt water treatment (with IAL added) recommended by you. I prepared this water 6 days ago in amoount enough to cover all 10 days of treatment. Sholud I use this water for all 10 days, or should I prepare new fresh one and add salt, IAL + dechlorinator?