Sorry, we should be getting back to you with some info. I'm not the best one for that though. I don't have a great deal of experience, and I'm in a warmer climate.
I don't think you should add empty supers to your hives. For a start, you are new and it is better to learn how to manipulate smaller hives, and then get a feeling for when another super wouldn't hurt. I think you'd be better off taking out some capped honey and storing it in the freezer for when you extract, and replace those frames with empty foundation frames. The hives that are low on numbers, reduce the space as needed to keep beetle and moths out, even if it means reducing space to a nuc box. Look at the brood pattern and if it is getting patchy your queen/s might be getting old. Though if you are sure swarms emerged from the hives, maybe the queen/s were replaced with young queens? I would advise not requeening all the hives, because that has its own risks...say getting 22 bad queens all at once would really knock your hives. If you are sure you need to replace particular queens you could also try killing the queen and making sure there are only eggs in the hive from your best hive. This sometimes doesn't work either.
Anything could have happened to the triple decker. If it had swarmed, the numbers might have been too low to fend off a pest. Always protect against ants, especially if you have meat ants there. Our stands have the legs in oil cans.
Adding pollen attracts small hive beetle, so I would only do this if it were a life or death situation (for me that is, not the bees!) In spring/summer conditions, usually there is pollen around even if there is not much nectar. Besides, there is not always pollen "around" the brood. Often there is just some on one of the edge frames in the brood chamber. Maybe with lower numbers of brood the pollen requirements are less so they are not bringing so much in. I live in a very dry area but I never panic about pollen. If you find a hive with nearly none and another with 2 frames, you can always brush the bees off and swap frames.
Feeding syrup is a desperate measure too. You might really need another site or two because 22 hives might be too many for what is flowering. What is the terrain like where you are? I would reduce the space, swap honey frames into the weak hives (preferably uncapped so you get to eat some capped honey too) and then see if you need to feed. Feeding might stimulate queen laying. Don't worry about not many drones. They will return when the hives are stronger and conditions better. There will be drones somewhere at ths time of year.
All the best, keep us informed, and welcome to you and Peter in Lithgow.