I know iodine does something with their glands and metabolism, but if they're ok now it'll be fine as long as you don't add more. When they go up and down up and down up and down it's like a boredom/unhappy thing, they're looking for a way out. Mine female did that until I could find a male. I still have an ornatipinnis that does that from time to time. Even looking on youtube it's fairly common, depending on how you tank is stocked sometimes companions can help, but not a guaranteed fix.
I always wonder if they know its time to spawn, or just exercising like a hamster in a wheel.