It's interesting that you mention Cyan from Precision Colors. I too always have problems with Cyan always clogging. I've been using Precision Colors ink since 2013 over 4 pro-100's with heavy daily use, and almost every other week I have to unclog the Cyan channel on all of them. There's...
Interesting you mention the Light Gray and Cyan, I actually had the same thing happen to me early last year on those same two channels but strangely enough, I was able to clear them both. The Cyan cartridge had developed the same odd stain I was talking about earlier too but it has since never...
Glad to hear I'm not the only one having this issues, I found this post after googling for some help regarding these clogs. I have two pro-100's and have gone through about 8 printheads in about a year and a half. All of them being the PM, M or both. I consider my use of the printers more on the...