Hello again, we are covered in algae over here.
Yes it is normal for nutrients in the water to go up after a screen cleaning. But after your rocks are covered in periphyton (http://algaescrubber.net/forums/show...-food-producer) there will be less up and down when you clean.
If you have light on 1 side of the screen, that is probably best for now. But I think your screen is too big for your feeding. If you want, you can double your feeding, or you can reduce your screen size by cutting it in half (up and down) and wrapping plastic wrap over the slot. This way it will be a tall, narrow screen.
Brush the screen weekly, and see how it looks in a few more weeks.