I have been making 1-2 quarts a day to treat one of my horses. I make it with the silvertron elite. Before the end solution would be a mild yellow color. My last two batches are dark grey. I have probably made around 50 quarts and haven't had a problem. So I am not sure what would have changed. I have it at the same settings. 80ppm, 1 Ma, quart M. My rods before would come out black on one and light grey on the other. Now they are both black.