Why is my plant growing stringy flowers?

That's not automatic...at least not that one. It's a genetics problem no doubts but that plant is re-vegging.

She's revegging.

Very poor genetics, quite common with autos. May as well leave it to mature fully and harvest then, no need to panic chop it, the results may be surprising. Looks healthy, unfortunately let down by poor breeding techniques by the seed company.

Look like "dr grinspoon" kind of phenotype.

Yes, it’s an autoflower! It’s outdoors so when the sun goes down, there’s no more light on it. I’ve got 3 others that look fine, albeit different strains. Should I let this one go to completion or cut it?

*If this is an autoflower, you can skip the rest. There's something fucked up with it. might end up with a dr. grinspoon look. i've seen something similar. smoked okay and was crusted with trichomes, but little individual calyx buds and loose foxtail/larfy top colas. otherwise, looks like it has re-veged. Something has interrupted it's dark cycle and it switched gears back to vege growth at least partially. the single bladed leaves are a tell-tale sign. your description matches up too. stem elongation and leaf growth.. if those things hadn't stopped yet, was merely early in process as it takes at least 3+ weeks after flipping to 12/12, and these don't look too far along. if you can read from a book, it's too bright and can interrupt dark cycle of marijuana plants, which will throw off the hormonal balance. This is how it can effectively tell time, at least relative to reproduction cycles. make sure it gets at least 11 hours of total darkness or it'll have trouble. 10 may even work, but 11 is safe. Extra is okay as long as it still has a sufficient DLI. looks outdoors, so maybe the length of day has changed? if so, you'd hve to cover it up a few hours at start or end of day. bad thing is you'd have some potentially much older bud development mixed in with newer bud growth... keep eye on it.. make sure nothing rots on the plant.