Pretty sure the brown stuff are diatoms, usually refered to as "brown algae". Most always get them after setting up a new tank, natural part of the process. Some tap water may contain with silicates which I understand are the main culprits, causing the diatoms to flourish. Mine came after about 3-4 weeks at end of cycle, and have decreased over last couple months. Got a little green now on substrate, but the brown crap still has to be removed from the glass now and then.
Phosphates/Nitrates + a lot of Light = large amounts of most any algae problem.
If nitrates are high, do water changes a little more often. If phosphates are high, figure out why and try one of the phosphate removers on the market.
Good luck ~ Brian