What's your light schedule. I've tried 24/0, 18/6 and settled on 20/4. I have an auto now that is stretched because I screwed up and had it too far from the light and it was not coming on as strong as other plants and I played with the light and it kicked it in to gear.
You may want to try either 12/12 or 18/6 to get them to come in to flower.
They are definitely tall, what strain/s are they?