About a year ago i noticed a color change on just one of the pex tubings. I have 2 units, miami heat pump 2.5 ton and a 3 ton compressor (2stage) in a 3.5 ton unit. The 3 ton is working flawlessly since i put a stronger pump a few months back. The 2.5 ton was working fine early in the year where recently it has started cutting out with low pressure lockout on heating. It suppose to automatically come back on and after 3 attempts it stays lockout till the computer is reset. It no longer does this. My delta t has always been around 10*. The temp. gauges quit working about 6 months ago and i havent replaced them yet, so i am only assuming the flow is normal. The color change is peculiar because its only the out line from the 2.5 ton. The pex on the domestic hot water changed to a brownish tint, but this is a seperate system. I used distilled water in the main coil. The pex has turned a grayish color. I am going to get some gauges and check refrigerant pressures, but in the meantime was wondering if anyone has seen this before. Pics included. My fear is a refrigerant leak into the water.