Well perhaps the WiFi antenna in this particular tablet just isn't as robust as it should be. Or there could just be some other issue that's the problem. Have you tried using your tablet elsewhere (i.e. a friend's home or at work) and does this same limited range issue occur there too, or is it just at home? That might help determine if the problem is with your WiFi at home or some problem or limitation with the tablet itself.
But really, you should at least start by rebooting your router and your tablet to see if the problem is still there or it was just a temporary glitch. Yes you mentioned other gadgetry in your household aren't a problem but networking is just not that simplistic -- the problem to focus on is the tablet's WiFi connectivity, not the other devices.
If this solves the problem, then hopefully is just a one-time matter. But if not or the problem comes back later, than it becomes a more involved project.
Install this 'WiFi Analyzer (open-source)' app on your tablet:
You can use it to measure WiFi signal strength and make yourself of basic 'heat map' of WiFi coverage in your household. Stand a few feet from your router to get a base measurement, then just walk around your home taking different measurements in other rooms further away to see just how strong or weak your router's coverage extends out to. Instead of assumptions and guesswork, use actual data to get a better sense of where there is good coverage. Be sure to check both 2.4GHz and 5GHz band -- in outer fringe areas you may find using a 2.4GHz band network is a better option (..... 5GHz can transmit faster bandwidth but 2.4GHz signals can extend further and penetrate through walls better, the issue being a strong 2.4GHz network is better to use than a weak 5GHz network.)
You might also want to check if just repositioning and/or relocating your router will improve WiFi coverage. If your router is currently buried under a desk and surrounded by metal file cabinets that will significantly reduce the strength of the WiFi signals it emits. Move it higher up and out in the open. But whatever the case, this is a good article on router placement that's worth the time to read through:
Bottom line though is to determine if the problem is that particular tablet or your home's WiFi.