Anyone else have a sulphur / rotten egg smell today in their basement after the rain?

I have a two-way plug in my basement drain to prevent sewer backup into my basement when it rains a lot. Yesterday, the plug was up, meaning that the pressure from the overloaded sewer was trying to push water into my basement, but it couldn’t.

Today, the plug is still up, but it now smells like sulphur / rotten eggs. I’m assuming this is a result of the overloaded sewer, but I’m not sure. Anyone else having this issue?