I read this post, in which the poster states that he believes it is a non-neutral ph which could be causing the bad taste he and others are getting.
I just tested the ph of the distilled water. It is very acidic, about 5.3 The test was odd also, it developed slowly with just specs that widened, not an overall 5.3 the rest remained yellow for quite a while. I did it twice.
I could add bicarbonate but that would raise the conductivity. I will have to try different water.