Leaves losing color and leaving spots

[Waira]

..roger that on the water hardness- ... Do you calibrate you pH meter, and store it in the right solution made for them? This is critical for preservation of accuracy and life of the meter, they are sensitive instruments!
...leaf look very suspect for infection now,... not uncommon, and if not spreading, you're good!

 

[OldGrumpy]

Could very well be an infection of sorts. Dried up brownish leaves appearing again. I cut them off and the plant looks healthy for a couple of days.