It looks alright.
Fin rot I caused by poor water quality or a dirty tank. The easiest way to prevent it is by having a healthy biological filter, doing big regular water changes and gravel cleaning the substrate.
Monitor the ammonia, nitrite and nitrate levels. You want the ammonia and nitrite to stay on 0pm at all times, and the nitrate to stay below 20ppm.
If you get an ammonia or nitrite reading above 0ppm, or a nitrate reading above 20ppm, do a 75% water change and gravel clean the substrate every day until the levels are back down to 0ppm. Make sure any new water is free of chlorine/ chloramine before it's added to the tank.