Waterbear, so you don't think its possible that the blue (that has a definite copper green cast to it) was caused by the copper that got put into the water when the heater copper on the heater was destroyed by low pH and is now precipitating out at higher pH?

I will definitely get a good look at the filter end caps. I presume when you say filter end caps, you mean the rubber/plastic that is mounted at each end of the pleated cartridges correct?

Thanks