It's funny you mention this, as I was thinking the same thing about mine. My resin is still blue, so I'm guessing it's stripping everything out (and my TDS
is 0 on the product water).
Here's my thread on the issue:
Like you, I feed 3x a week, and I don't go dumping in a whole cube of PE Mysis, I thaw it, and then drop in a couple for my clowns, one for the cleaner, one for the goby. I use a little (about 1mL) of the "shrimp juice" once a week as a treat for the coral.
The only thing I can think of for my tank is that in the beginning, I didn't have "reef" lights on the tank, so I'm wondering if I'm going through the ugly stage now since I have a more powerful set of lights running. Did you upgrade your lights anytime recently?