I think a lot of people forget that a lot of this is just best guess, and the way that a lot of people run their systems too clean, some people starve their fish and only feed once or twice a week to chase 0 nitrate and 0 phosphate. As long as you have a skimmer and/or macro algae to help take away some of those so your numbers are not too high, having some stuff that coral can get, is a great thing. People see algae as a horrible thing a lot of the time, yet if you talk to a lot of people, even ones running SPS systems, when they clean their glass, and those pieces of algae are floating around in there, they get better polyp extension than they see most of the time.
All of us have different systems, and different methods of achieving the same thing, look at Paul, his system has been up 40 years now, the equipment he uses, is not what most of us would ever suggest to use for each other, but his system is thriving. Do not be afraid to try little changes like this where you remove filter socks for a few months and see if things are working better for you, you can always put them right back in, just do not change 50 things at once, or do them every couple of days, everything in this hobby that is worth happening, takes time.
Do you think that may have been it? I'm telling you. When I ran the all the time I always had things going on that I couldn't explain while the other systems were completely fine and thriving 
