I'm afraid you'll be waiting a long time for the plecos to clear the brown algae, unless you stop feeding for a few weeks and they get desperate.
!Algae eating fish" don't clear up as much as you'd think in my experience. Best bet is to clean it all off, and then hope that they can keep on top of any new growth. If not, try to establish the caus eof teh alage and correct that :thumb:
I would just wipe it. I have a long brush which comes in handy since my tank is over 2 feet deep. The best algea eater I've had is a Siamese algea eater. I may rehome my pleco ang get more. Also they are very active