Sounds like your tank has not fully cycled. You have nitrite, but not nitrate? Nitrite is toxic to fish. You want both ammonia and nitrite to be at 0. If things are all cycled and ready, these won't rise again. Ammonia and nitrite should not be a maintenance issue in a planted tank, once they reach 0, they should not come up again unless you have a mini cycle, or you're overstocking.
Please describe your CO2 setup. Since your diffuser just shattered, you are not getting CO2 into your tank at this point. Might I suggest that you try running a reactor in-line? Try here for DIY instructions or to buy one: http://rexgrigg.com/diy-reactor.htm
It is important that you get CO2 back up soon. As mentioned above, 192 watts is a lot of light not to have CO2. You should also begin a fertilizing regimen. Algae is not caused by fertilizers being present, it occurs when there are nutrients that cannot be used. Plants require light, CO2, macronutrients, and micronutrients. Light drives everything, as stated above. The next most commonly lacked thing is CO2. If you don't have enough CO2, plants cannot use the other nutrients. Once you have enough CO2, you must have enough of each macronutrient (NPK, nitrogen, phosphates, and potassium). Think of these as plant food. Finally, there are micronutrients. Think of these as plant vitamins. All are necessary for healthy plants. If you run out of, say, nitrates (nitrogen), your plants will not be able to use the other nutrients. However, algae CAN use those nutrients, hence the problems occuring.
Finally, how long have you had this setup? If you have brown algae, it sounds like you have diatoms. This is common in newer tanks. You might want to get some otocinclus catfish. What other fish do you have in the tank right now?
I recommend taking a minute to read these 2 excellent guides: