Female hairs first start to show at each internode...where the branches meet the stem. They will be very obvious...about 1cm long by the time they stop growing. Are you sure you aren't looking at the very tiny hairs that cover both male and female plants? Leave any plants which don't show the balls in that close up photo. If it were female there would be a single hair 1cm for each of those ball sacks.
It probably wasn't stress. It was probably a male seed. That is why you were asked where you got the seed. Reputable seed companies do occasionally get male plants from fem seeds, but not very many...so good to know what company the seeds are from.
Edit:
Ok just re-read your last post. How did you sex them, and how long ago did you see these female pistils before the balls started showing? Do all your plants look like that or just one.,..
