Note today's date. The sun is low, soil is coolish (even in GA). The plants are not getting enough energy to grow the way you are expecting.

I agree with above.

Cool crops can survive cold and frost but that does not mean that they will grow in cold. Of course, there will be some variations among them. The trick with planting them is to start them early, so they will a chance to grow before it get real cold. And that can be tricky. Like in North Georgia, you plant them in mid August. But if summer weather carries on til October then some may bolt. But if you are lucky and it starts cooling off then they will grow nicely.

Should not be a problem. Broccoli, cabbage, collards. cauliflower growing well here. Fluffy rich compost mix, watered daily may be the problem. These plants like heavier soils and deep watering maybe once a week.
Transplanted late September {{gwi:118545}}

Also store-bought starts if they were sitting too long in the pots can get kind of 'stuck'.

Last year I was late getting my carrot seed in the ground. It was in October when I sowed. My carrots grew, but oh so slowly. It was December before I started harvesting them. This year, I sowed carrots the first week of September. It has made a huge difference. I am very close to harvest size now. Perhaps timing was your problem? (I was late getting the beets sown this year due to space availability. Guess what? They are growing very very slowly. I may just get beet greens this winter, which is actually okay. but, as you can see, timing can be everything this time of year.)

Brassicas (broccoli, etc.) are heavy feeders. Perhaps they could use a nitrogen boost? Also, take a look at the sunlight levels they are getting. The sun moves in the sky in the winter and plants that are in full sun in summer are sometimes getting more shade in the fall and winter. Broccoli likes full sun.