Is ketoconazole shampoo 2% safe for dreadlocks?
Dread Products
Honestly, I don't think you are ruining your dreads. How about going off of the medication for a while and solely using the tea tree rosemary bar. The rosemary is good for fighting dandruff and the tea tree is also an antiseptic. Wait a couple of weeks before evaluating the scalp because changes in soaps may take a little bit of time for the hair and scalp to adjust. If your scalp reverts then you may have a strong case of seborrheic dermatitis and you can certainly ask your Dr. if there are other ways to control it or other shampoos/rinses she can recommend that are more natural.
I've also heard that a person's diet can play a part in it because of yeast production but I'm not 100% sure on that. You may need to do some research on holistic ways to treat it.