All the crash logs attached are low memory jettisons. We need to make sure the pages in your issues are optimised as much as possible to lower the memory pressure on the older devices. Either by making the PDF files as small as possible, both quality wise and physical pixel size, or if they're html pages, make sure they're not overly complex.
Also make sure the apps are on the latest version of our core code base. There was an issue a couple of releases ago that could cause a crash on older devices which is fixed now.