I doubt its lighting. If you had better lights you'd just have green instead of brown. Light doesn't cause algae, conditions do.
What are your water parameters? AM,NI,NA
I'm guessing its either high nitrates or high phosphates, which you can't check for unless you buy another test kit. Since you have city water I think you can call or email your city water company and ask for a water breakdown report. It'll show how much phoshate, nitrates, iron,chlorine, etc is added to the water.