One out of three not producing

This is my first tent grow after 3-4 outdoors. I have three Auto CBD plants in a 2'x4'x5' tent with a Spider Farmer SF2000. The plants are in good soil in 3 gal pots. My problem is that one of the three plants is not like the others. Two are very healthy and producing nice buds (at 8 weeks). The third is very thin, scrawny and the buds are not developing. They have all had the same light, nutrients and water. Could this be something that I have done wrong in handling the plant? Could it somehow have been contaminated or just bad genetics in that seed? The seeds were all purchased together.
I'm on a 18/6 cycle and humidity is 62%, temp 23C.
I think that plant is a write off but if there is something I could do to bring it back I would definitely try.
Sorry for the fuzziness of the image but you get the idea.
Any input would be appreciated.
Thanks.

every once in a while i get a way different outcome from plants, same soil same water same everything, one thing i've noticed is some times you get the runts if you will, some times i grow them out if i got room some times i cull them, its up to you if you can't find a reason why said plant is different