If there is a significant difference in sunshine exposure, leave them outdoors. 21/9 is a typical late August pattern where I live and it does not impede eggplant fruit production all that much. They are more sensitive to cold during the early vegetative stages of growth. You can try to create a warmer microclimate around them by laying the containers on a sheet of black plastic or other black surface. Besides, your concrete balcony will be much warmer than the officially recorded minimum temperature near the ground.

alberta, I closely watched the two pepper plants last year and luckily didn't get any infestation. I also pruned them back a pit with only 8-10" of main stem and a couple of side branches. I also kept them pruned back to a few set of leaves while indoors. I will have to be more vigilant this year as I will bring more plants in and looks like I already have spider mite infestation on the beans and tomatoes. Maybe a horticultural oil spray before bringing them in. Frank - I started the eggplants last week of Jan, but they don't put on much growth inside. Outside also, they don't start growing till it has warmed up nicely. I did notice very vigorous growth in the one extra seedling I put in a SWC at the end of June. It is already outproducing the inground plants planted much earlier. I did put out a couple of early tomatoes very early ( two weeks before last frost date) and had tomatoes last of week of June. Not sure if it will work with eggplants.

You have the wrong Forum but you can overwinter them. They are much stronger than pepper plants. People do it all the time.

Dan, I'd keep it for at least a couple more weeks before deciding to pull it. Ours were flowering for what seemed forever (a couple of weeks) and even dropped a good number of blossoms with no sign of fruit and then from one day to the next there were suddenly a handful of tiny fruits forming and we've had the "big fruit bust out" starting only in the past week and a half. They are still flowering and fruit is still bursting forth. If the plant is healthy and flowering I'm betting you will soon be getting fruit on it!