I agree. Obviously we don't know what he looked like before but I don't see anything wrong. Try searching online for images of male Bettas and you will see plenty that look like this.
As such I would avoid adding any chemicals, including salt, as these always stress your fish so should only be used if there is a definite problem that needs to be fixed. Likewise large water changes should be undertaken only when absolutely necessary as these too can be stressful. That looks like a good sized tank for a single Betta. If it's established and your nitrite and ammonia are zero I would change 10% a week, using a gravel cleaner.