Finches wasting huge amounts of seed

I've got lots of finches coming to the garden, but they are going through seriously huge amounts of sunflower seeds every day, which is working out to be really expensive. If they were eating it all that'd be fine but they are chucking at least a third of what they eat on the ground. I'm feeding them sunflower seed hearts. I feed them from two squirell and big bird proof seed feeders (the kinds that a cover comes over the ports if anything too heavy tries to get onto the feeder). I've got loads of greenfinches, a couple of chaffinches, and a pair of bulfinches, all of which mainly use these two feeders. Whilst this is great for the 4 dunnocks that I have in the garden, which just won't seem to go to the bird table, basically it's mainly feeding one fat pigeon that sits around all day waiting for them too come and chuck his dinner to him. Whilst I have no problem with pigeons, I consider that they can fend for themselves, and i don't wish to pay rather a lot of money to make them any fatter than they already are. I've tried chopping up the seeds in a food processor but that didn't appear to make things any better. I'm wondering whether giving them sunflower seeds without being husked would be better, as I suspect that what's happening is that they're "husking" the hearts? I know that I could put down a tray etc to catch the fallen seed with a guardian over it to stop the pigeon getting to it, but I don't want to put it back into the feeder as they poop on it at the same time as chucking it out and don't want to introduce bacteria into the feeder tube, and they throw away so much that the smaller birds wouldn't keep up with clearing what they waste. The one good thing is that at least they're not encouraging rats as the pigeon does clear up the mess, but I'd rather have a way to stop them producing the mess in the first place, if anyone happens to know of one. I've got a great lot of birds in the garden and also have a covered bird table (protected by a guardian), which I put mealworms and sunflower seeds into, which mainly attracts robins, blue, coal and great tits. 2 hanging mesh peanut feeders, which get tits on them, a plate which is covered with a guardian with mealworms only which gets robins and tits and a hanging seed feeder with a guardian with kibbled peanuts which mainly gets blue and coal tits. I've also got a niger feeder, which had a couple of gold finches too for a couple of weeks, but they've dissapeared now. I've got a hanging bird bath with stones in it for different heights and a ground bird bath, again with stones in it for different heights.