It turns out Mike Hurley was wrong
It turns out Mike Hurley was wrong
Ding, ding, ding, ding!!!! Someone on the other thread called it red cotton algae, and his was caused by overly old RO/DI filters.
Well, so it turns out Mike Hurley was wrong: zero tds isn't zero tds!
I had focused on that number. Tonight I looked at the filters. Not only were they black, but the housings were coated in green algae. Yuck. Couldn't seem to get the membrane out and with no spare I didn't want to chance it (how are you supposed to get that sucker out of there, anyway???). But flushed it real good -- 15min. Hopefully whatever was in there is also gone.
And now I have 5 brand new cartridges going, in clean housings.
Let's see....