Grantparent poster here. Hrm, you're right, I remember purchasing keys 'lighter' than browns, possibly silvers. They're very light, but I'd probably prefer 'too light' over 'too heavy'.

You may have Gateron Clears, which are lighter than Gateron Browns. Gateron Browns are basically equivalent to Cherry MX Browns, but Gateron Clears are entirely different from Cherry MX Clears. This has tripped me up more than once.