That because those devices have a least 512mb ram, iPods only have 256mb ram (except generation 5 have 512mb ram). That means you only have about around 70mb ram to work with. So scaling down from iPad 3 have taken too much memory, due offbuffer take a lots of memory.
Rapids Rider did also suffer same issue, so they forced to remove the screen wipes to safe memory and then works on iPad 1, which also only have 256mb ram.
So you property need to rescaling down by factor two and load those textures directly. In my own game, Genius Greedy Mouse, uses 3 sizes of textures (except few graphics), which was to save ram. Howover It's take a lots of file size, but better that than use more ram.
So in the end, you simply uses too much memory, so it's crash because you can't fit and resize all graphics used.