I have had my betta since about January now and I have just noticed his fins are starting to tear and disappear. I do give his tank weekly cleanings as well as the usage of water conditioner. Does anyone know what could be the cause of this?

I did try to google this (I found he has fin rot) but the treatment options were all over. I found just feed him certain food, give him medication, or simply just clean his tank out more frequently. Which would be the best option to proceed with?