Polyp extension related to activated carbon?

[Stones]

I have been doing alot of thinking lately as to why several of my milleporas are showing poorer polyp extension than normal and the only factor that I've changed in my system is that I switched brands of activated carbon and now I am running more carbon than previously.

Has anyone else noticed such a difference in PE while using or not using activated carbon? My milles used to have such crazy PE that you could barely make out their actual shape, but now you can see their whole skeletons and the polyps only extend maybe 1/8" max.