I don't think it's algae but not sure what it is?

[Bluechip]

Our pool is just over a year old and has been BBB for it's entirety. Over this winter (not closed) I started to notice that some of the pop ups for the in floor cleaning system, intakes and drains have developed a light coating of something brown. All of the parts are plastic and I was just thinking that they were discoloring from the sun. I tried to brush it off with out any luck. I dove down and wiped it with my finger and most of it would come off. With a washcloth it comes of pretty easily. It does leave a light staining. It's mostly the plastic parts that are in the deeper section of the pool. The shallow end and the spa do not have it.
My chlorine usage has been normal.

FC 5.5
CC 0
CYA 40
ph 7.6
CH 310
TA 70

I added a picture and you can see where I rubbed it to get the brown off. (By the way I am saying that it's brown because that's what my wife has told me. I am red/green color blind and could not tell what color it is.)

If it's algae then I guess that I am looking at my first ever shocking process. Yay!

 

[BoDarville]

I think it's just a fine layer of dirt/dust. I get that occasionally, especially after a heavy rain or extremely windy conditions. Having a pool makes one aware of how much stuff is either washed out of the atmosphere during a rainstorm or blown about in windy conditions. This film is likely spread out across a larger area of the pool than it appears. It's just more visible on the plastic parts due to their white color and the fact that plastic is somewhat porous.

 

[Bluechip]

Thanks- that's pretty much what I was expecting/hoping, but it's good to get a more experienced opinion.