Yes, that's completely normal; it has to do with genetics. Each plant has a slightly different genetic makeup and grows accordingly. You can have the same strain, and still, one will mature faster than the other, and the buds will be denser, etc. But the thing with the seeds is normal too and doesn't mean they're older. I recently had 2 strains, each with 2 seeds, and both germinated with a 1-day difference for both strains. Then there are seeds that just take longer, up to 7 days, but if it takes longer than 10, then something's wrong. Good luck with your ladies!