it can means your calcium level is not stable. Are you using the RO
water? cuz sometimes water change helps algae growth as a lot of nutrient will replace by the new water that put in.
Having a stable KH
is always important for the health of your fish and coral. Here is something I can suggest that you can give a try.
1) use a new toothbrash try to remove as much hair algae as possible.
2) limited the feeding down to no more than once a day or even stop feeding for may few days
3) Limit the lighting period down to about 3 to 4 hours at peak and no more than 6 hours.
4) try to keep your KH
stable and calcium level stable.
5)You can try this but only when you think you are ready, you can buy a sea hare and try to have it to clean up your hair algae, and once it has done the job, you will have to pass it on to someone else or return it for store credit as it will starve to death without hair algae. You don't wnat it died in your tank as it release toxin