More waterchanges to siphon it out, cut back on feeding, skim wet, increase your flow to that area, replace your bulbs if they are more than 8 months old, and ohh yeah dont give up i have seen worse trust me.
What causes it to grow is high nutrients and phosphates. So skim wet to remove more nutrients in the water and do water changes with good RO/DI water and get some kind of phosphate absorber. Cut back on feeding so you arnt adding extra waste into the tank to break down and cause problems like this. I feed my tank every other to every 3rd day.
I have been doing what you suggested for about a week and I am wondering if anything is helping. I even added a phosphate reactor the other day. Frequent 10-20 % water changes. Use good R/O for top-off. I use catalina water as my usual saltwater. Cut back on feedings to every two days. I'll try anything