Help a WC noob, why has my fluid turned yellowish/orange.

[Trigger5521]

I noticed my clear fluid starting to change color after 6-7 weeks. Upon further inspection there is red guck in the fusion block of my striker II extreme. Sticking a Q-tip in the port it comes out red. WTF I thought I did my homework..no mixing metals. My RAD is cooper, my CPU block is copper...the fusion block is copper.

Questions...what causes this...is it the nickle plated barbs?

What's the best way to clean out the ASUS fusion block? what should i use, is rubbing alcohol ok?

I used Primochill PC Pure fluid if that helps.