Sometimes I find a slight variation within a clump of blooms. I am wondering if it is very likely that it is a self sown seedling, and if so, can't we just sow seeds outdoors in a similar fashion? Or is it more likely that it is a natural variation, or weather related. I think I will separate out any fans that are different and plant separately and see if they keep their difference.

I think it could be either. I have seen the slight variation in bloom in cultivars that never produce seed pods for me. I also think for those cultivars that do produce pods, a seed could fall and produce a similar flower.