Possably the seeds pollen sources were different

I do not think any sativa will flower in under 50 days sorry. You could take acouple of the small nugs that are not going to be much off a couple days before and smoke some of it but it will be very premature. I have harvest a sativa at 50 days but it really needed four more weeks on my first grow indoors ever. I would have gotten twice the yield if I waited but owell. It was a great pure high.

I would guess a 8-12 grams yeild on the tall sativa and possibly more on the other smaller plant with more light. The high will be excellent though so no worries you just need to grow more and keep them shorter.