i'd say the first step is to move to RO+DI water.....there may have been an adverse change in the TDS of the water coming from the tap that may explain why you had less algae then and way more now.....in Toronto, TDS direct from taps can vary from 154 (my tap) to 250 (my buddy in oshawa, just to the eats of Toronto).....you need to have water with 0 to 4 TDS (the range I aim for).
definitely move to RO+DI water....that's the #1 source for phosphates - the main food for algae
also increase your flow (yeah i know you have two SEIOs) try and keep your detritus in suspension, so the skimmer can get to it......and use a turkey baster and blow water at the rocks, like, everyday....until you're sure there is no accumulation.
this is just a start....
good luck!
Zach.