After the first 4 weeks you should be dosing the tank with ferts.
you make no mention of your lighting levels, so I can't comment on Co2 or fertilizing until we know lighting type, and wattage/intensity.
Even with a perfectly setup system you will likely get spot algae on the glass. Just scrub it off.
I have hard water so I don't dose Mg. I get pure KNO3, K2SO4 and KPO4 from Curt at www.plantgeek.net
You can also order from www.gregwatson.com