Very strange. Took a course last year entitled 'Ecology & Evolution', which I highly recommend to anyone growing cannabis and into breeding. This looks like an altered genotype caused by a random mutation.

The mutation isn't necessarily bad, since it hasn't appeared to cause the plant any harm (as of yet). In fact the mutation is neutral or good, if anything. The mutation has contributed to the plants' fitness, since it's the only survivor of the adverse conditions (whatever they might've been) that caused your other plants' death.

I'd suggest keeping it, cloning it, propagating it. I'm excited to see what will become of this plant.

Keep us posted! :thumbsup: