Curiously that’s not as accurate as you might think. Different systems use memory differently, even just between different Ubuntu flavors or customizations. 1-2 crashes a week is not normal, unless it was consistently happening when you did something specific. Also, what exactly do you mean by crashing? Did you get a black screen with some error or the computer would just freeze or reboot?
That being said I don’t think this is likely to be a hardware issue. One thing that comes to mind is maybe swap, did you had swap on Ubuntu and do you have swap on Fedora now? If Linux runs out of memory it freezes, having swap prevents it from doing so, so if you have low enough memory it’s possible that it would get filled up and freeze your system without swap (Windows has the equivalent by default)