Algae?

Brown is usually diatoms. Often found in cycling tanks as light and even trace amounts of ammonia encourage it. Check your ammonia level, and the length of time your lights are on.
Just scrub the brown off under the tap. I have a cheap toothbrush I keep just for scrubbing things. The amont of chlorine (from the tapwater) you'll put back in the tank on decor is negligible. And yes, fish will eat it.

Even trace amounts of ammonia, too low for our test kits to measure and certainly too low to harm the fish, can stimulate the growth of diatoms. You could try Chucklett's method: reduce your lights-on time by 15 mins a week until the plants seem to be stretching towards the light, then increase back up by 15 mins and use that light duration.