I don't think CRUD,a name I almost regret coining,
, b'c CRUD usually is seen as browning along the entire leaf edge and I've seldom seen it on PL varieties either.
One other possibility is fertilizer tip burn.
Another possibility is over watering.
Varieties do respond differently to fertilizer, to water, and to other things such as BER susceptibility in fact, so it doesn't bother me that it's only two varieties affected.
Cathy, at this point I wouldn't worry about it that much, If the situation changes, do let us know.