I had been using tap water here in Athens (ph at 6.5-6.8), where it is enriched with chlorine and contains A LOT of lime. I noticed a few stains on the leaves and some residue on the aerial roots of my phals, which eventually dries them out starting from the tips and moving up. Later on I discovered that only older roots die off due to the residue and that new roots grow without any problems.
I occasionally top up the s/h containers with rainwater (ph originally at 6.5, buffered down to 6-5.8) and fertilize. Surely there's some difference between tap and rain water that the plants respond to, but I'll know for sure in another 6 months.