If I have a Solrock in play so that Lunatone's "Heal Block" ability is activated, does it apply to all Pokemon in play or just the two active Pokemon?
It applies to all Pokemon in play.
Source: Burning Shadows FAQ (2017-07-20), TPCi Rules Team (2017-08-03)

Relevant cards

Note: All applicable cards may not be listed below.
SM3_68