Some updates, accidentally discovered that Joe's juice can actually get rid of these algae. I spray a small amount on the affected areas and the whole patch will slowly die off after a few wks. Need to be careful when applying on areas near corals. Would suggest diluting the juice in aquarium water or di water before using. I didn't and actually end up injuring some of my corals but its recovering. Almost immediately after applying, the thick slimy mucus covering the brown wafer algae will be gone and after a few days, the brown patch will turn dark green. A wk or 2 later, it will turn white and coraline algae will cover up over the bald patch.
Cheers.