Growth differences between two of the same plants

Yes, it is completely normal for each and every seed to grow differently, even if they are the same strain and the seeds came from the same packet. Each seed is an individual, unique organic being with unique genetics, and, a bit like children, even though they may have the same parents, due to gene recombination, all children are different, so it is so with seeds. Breeders who grow the seeds for you and I to purchase, possibly have hundreds of mother plants they fertilize, meaning although the parents are of the same strain, slight variations in genes occur in the seeds. Not great variations, but some, therefore, while you and I get plants of the same strain, we also get varied offspring that are true to the strain, but are unique individuals. Fertilization is a random process which allows for various dominant or recessive genes to recombine and this is what causes the slight differences in the expression of the plants. This is also why, once in a while, a "super" plant will emerge that has special features or enhanced characteristics that make it that "one in a million" individual that becomes legendary and the envy of every other breeder. A bit like "Critical Bilbo", whereby there have been tens of thousands of "Critical" plants grown, but only one "Bilbo" version. Hope this helps,........... Organoman.