Apparently there are 4 juvies! Another fledged and landed on the glass balcony so they picked her up and are keeping her for banding before putting her back.
Toronto seems to revel in glass buildings and glass balconies. Problem for our falcons is they don't understand glass so they try to fly through it. We had to take two off glass balconies last week at our site - not because they were too low either, they actually stayed high and landed on upper balconies but couldn't figure out how to get through the glass to take off again.