I have several on both my ac units on my fiver. But my condensation runs where they are. I figure it's pollen or other dirt in the air mixed with a little bit of alge.
But, we are at a seasonal site and have used it about 34 nights since we took delivery of our new sabre, and we live in humid Oklahoma. So we have had LOTS of condensation running off the roof.
I will try to remember to get some pics tomorrow when I stop by to inspect for hail damage.
Might see how mine match up with yours. I'd defiantly be concerned if its not like what I think mine is from, being as yours is almost out of warranty.