Phil, when I tried Aquarelle, I tried both an oxcalic acid and citric acid bath and got the same result. The blotches I got were most noticable in the highlights and mid tones, but were present throughout. The blotches were definitely caused by the Aquarelle paper as a different batch of paper processed in the same chemistry at the same time came out just fine. I'm convinced it's the sizing.

Regards, Pete