How old is the tank? I get waves of algae the first year or so a tank is up and running. Beyond that, any increase in nutrients (either via increased feeding, or the demise of any inhabitants) or change in lighting tends to cause a small uptick in algae for me. Did you change the carbon and GFO before or after the increase in algae? If you've been running them on your system, and they needed to be changed out, an increase in glass algae would be entirely natural and expected. If that's the case, it should decline now that you've changed them.
Other things to consider: any recent demises in the tank's inhabitants? Trapped food, or fish gone missing can decompose and cause a nutrient/algae spike. Similarly - how's your CUC? If your levels of snails or other cleaners have gone down (either through natural lifespans, or predation from hermit crabs, not enough to eat, etc.), you might notice more algae just because it's not getting cleaned off.
