is Big Pink a cross between a Red and an Alba
I believe so.
Here is a quote from Joshua Lynch, the discoverer of 'Big Pink'.
I germinated seed from my Albino cape sundew and a few of the seedlings were different. They flowered 6 months from germination when the other seedlings took 8+ months. They have pink foliage and are 10 to 12 inches across, about 30% bigger than the other albino seedlings. Please check http://www.flytrapking.com for current availability.
Maybe it was a spontaneous mutation.
Maybe an unknown pollinator appeared on the scene with some excessively healthy Red capensis genes.
I bought my 'Big Pink' from FTK directly, a few years ago.
It flowers every year and I usually toss the seeds into the Cape Sundew variety packs.