Hopefully you also had a SMB spawn this year, and the SMB just need to get a bit bigger and you will start catching them too.

Is your water generally pretty clear in the spring? If so, there is a chance your smallies might want to spawn a bit deeper than 4 feet.

OTOH, with all of the big Kansas rains this year did you have a bunch of silt wash in during your expected SMB spawn? I think with a couple of weeks of muddy water it is possible to lose your entire spawning class for the year.

Looking forward to more good fishing reports from your pond!