Check PH is always first in my book. Make sure your in VPD range, a good app I like to use is Dr Greenhouse VPD calculator. After verifying PH and Environment are on point then look into deficiencies. My guess is because they are in week 3 they are getting picky and either your PH or Environment is out of whack. Hope this helps.

The dreaded winter grows. I feel your pain. I tend to run 24 hr veg to keep temps reasonable in winter. From my experience cold temps tend to cause short plants because they never tend to get that vigor from higher temps. All you can do is try your best the plants will adapt and make harvest. Keep it as close to 75 as you can.

Cheers

She’s healthy and growing. No reason to pull her unless you want to replace her with another auto with hopefully more vigor. Not ever seed planted will have winner plants.

Most of the time it is bad growers. If growing with feminized seeds, this means seeds come from a herm plant. Coming from a guy who has spent weeks pulling nanners and nuts of a haze plant to make it to harvest one time. Just throw everything associated with that one plant away. Check for light leaks or any other heavy stresses in flower. And try again.