Looks to me like you don't add any phosphate to the water. If you're dosing Nitrate and all the micros with CO2 and high light then maybe a lack of Phosphate is causing issues? One part of the plant's needs missing will stop higher plants growing which will allow the algae to grow.
What is the level of CO2? I know many people say anything over 1 bps is fine, but some people swear by a level of 30ppm measured by a 4dKH drop checker. Maybe more CO2 might help? It may increase the plant growth.
Do you follow EI methods with a 50% water change or is this a method without the large weekly water changes? If so maybe upping the water changes and halving the doses for a week may help. The plants should have reserves of nutrients that will keep them going whereas the algae hopefully won't have so much!
Finally what plants are in there? You mentioned Crypts (which will grow back after melting BTW) but have you got any really fast growing stems to soak up all the nutrients? Maybe adding some fast growers, or even fast grwoing floating plants, will help up the plant biomass and reduce the algae?
Sorry there's no easy answer. Maybe the info over at http://www.aquaticplantcentral.com/forumapc/ might be more help, especially in the algae section?
Edit: I just looked again and that's a lot of Magnesium you're dosing. Why so much? Especially with your hard water as GH is generally made up of Calcium and Magnesium salts.
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