Setting a different debounce or delay for a single switch isn't possible in QMK firmware (and neither is it in VIA since that doesn't do anything different from QMK on the hardware side).

You have one value in the firmware config that is applied to the entire switch matrix scanning.

 

And since OP said that the issue went away after bending the pins of the switches it seems that this was simply caused by a worn out contact in the socket.
And not from a firmware issue.