What happened to Sheldon's IQ?

[Ratman77]

I have a theory: that the less time Sheldon spends with Penny, the dumber he gets. He's around people now all the time who are smart! But who like to act like he's an idiot... So he doesn't use his brain ever anymore. Around Penny he has to think... Penny makes him smarter! That's my theory.

Or Amy is a knowledge sucking leach who renders her host listless and stupid... One of the two.

Absolutely right!
 Penny and Sheldon were always been challenge and inspiration at the same time for each other. Both, emotionally and rationally they were black and white, -ying and yang- …..bringing only the best from each other to the fore . Now they are only the mindless appendages of there sooooo perfect partners of them.