i only have one cuttlebone for 8 parakeets. admittedly its bigger than usual, because i dont buy them as singles, i buy 3 at a time, and theyre not prepacked. they never fight over it. 2 mineral blocks- i think they could even do well with only 1, its just that i had 2.
i think mikes keets just need to establish a pecking order. theres no reason why 2 keets cant share 1 cuttlebone, unless theyre seriously fighting. not the funny play fighting that his are probably busy with. all 8 birds of mine share 1 feeder and 1 water source, which are of course big enough, but still- there are never any fights.