pH levels in low ppm waters are dependent on the amounts of dissolved Co2 to determine the pH value at that time.
Ultra low ppm waters have trouble "holding" a pH value.
These waters do contain less Ca compounds that normally "buffer" the water, and thus reduce holding pH value power to these waters.
Lack of buffers in RO mean you should add a Ca/Mg as a buffer to the RO/evap recovered waters before use..
ALL my water recovered and pumped to my RO holding tank. It is then used on all plants....Oh, blow by water from the RO is diverted to the chicken pens, and the outside critter water tanks...No waste here.