their hood light is on from about 10am-9pm
Try cutting it from 10-4pm. You're giving the tank too much light, it sounds like.
If the brown algae is like a very fine 'dust' coating or slime, it's likely to be diatom buildup.. they love light and too many nutrients in the water, so clean as much of it off as you can and then cut your lights out altogether for a few days (this will not hurt your bettas/plants any but it'll mess the brown stuff up!) and also watch you are not overfeeding.. definitely good to increase your water changes a bit, to flush out any excess nutrients, I find that helps to starve the goo/dilute the stuff they feed on.
Is you tank new? If not, it might be going through a mini-cycle, diatoms just love cycling tanks.. so keep a close eye on your ammonia/nitrite levels, too.
Here's some info on them (it's for saltwater tanks, but they're the same thing..) in case you'd like some : http://www.aquaticcommunity.com/aqua...ad.php?t=60144
(Sorry, OFL! We cross-posted! ><)