Download this small utility, TCP Optimizer 4,
and compare the readings on each User. It's not an installed program. Right-click on the TCPOptimizer.exe and choose open as Administrator. Once open, you'll see a drop-down arrow, make sure and choose your wireless adapter. Once that's done, look at the general settings tab and the advanced settings tab in each User account. See if there are differences.
You can even choose Optimal and tweak your settings if you want. It gives a choice to save before the tweak is done so you can revert if needed. You'll need to reboot after tweaking.
This is another utility I have used since Windows 98 without issue and with success in some cases.
PS: You'll need to run it each time as an Administrator.
This utility modifies the registry and as such, I would create a Restore Point before use, just in case.