The BlackHead mutation does not act as a “cure” for Spider. The allele, which has been proven allelic by scores of breedings from many different breeders, is most easily thought of as being like an “equal but opposite” mutation to the gene.
Again, a quick analogy: If we think of a WT as being warm water then the Spider mutation is cold water and BlackHead is hot water. The cold and hot, when expressed together, result in warm.
But the median state only exists when both alleles are present. So when a BH/Spider breeds out all the Spiders from the clutch, having only the Spider allele, will express associated secondary phenotypes. So a BH/Spider x Spider pairing will not suddenly give you live SuperSpider.
I issued a challenge a few years back to a group of people that adamantly refused to accept that SuperSpider was lethal: Do BH/Spider x BH/Spider pairings and prove me wrong on the outcome of the clutch (SuperBH, BH/Spider, and either nothing or dead babies)… Funny enough, no one was willing to accept my challenge 