Posted: 13/12/2014 at 07:58
Odis, it would help, as Dove suggests, if you could expand on "sickly". The photo isn't very clear, unfortunately, but the inner flesh and pulp doesn't look nearly dark enough for a black variety.
As for plant size, heirloom plants are always capable of variations, even including fruit size. Hybrids will grow identically but heirlooms, with their pure genes, are capable of hiccups.
If cross-pollination occurs, the results will only manifest in the next generation. If, say, the cross happened this season, you would have to save this season's seeds and plant them out next season to see the result.