Should I add limestone, crushed coral, etc. to my bark mix?

[varda.elentari]

I'm planning to repot a Paph and a Phrag (unknown varieties) that have been growing in sphagnum to bark mix. Those of you who grow these two genera in bark, do you add limestone, crushed coral or something to raise the pH of the bark? And if you do, at what ratio? These plants have been sorely neglected for the past few years so I'd really like to help them do better. Thanks in advance!