Sometimes algae just happens. But with that in mind, there are a couple things to make sure of first.
at 14-15" above the water, your light probably aren't *too* bright. However, your bubble count is useless to anybody else because of all the factors involved. So how's your drop checker? If it's at least solid green, pushing toward yellow, you're probably fine. And your ferts are probably fine as well.
Also, how's your water flow? Any powerheads on top of the canister?
And, while you dose EI, do you do 50% water changes weekly, as per EI? Just checking - a clean tank definitely helps.
I've had excellent success with spot-dosing Excel using a syringe (available at any pharmacy for a couple bucks). Just turn off the water flow, squirt a double dose on trouble areas, let it sit for 15 minutes, and turn the flow back on.
API Algaefix is also an algaecide that some folks have had success with.
You're probably overdoing it with the KSO4, but I'm not sure that's a cause of algae - just unnecessary for most folks.