Trolling and only caught small crappie

I was trolling for crappie and this time only caught small (4 to 6 inch) size crappie. I know there are larger crappie in this lake, but this trip could not find them.
So....my question is do the small crappie school with the larger ones so I just wasn't getting the larger fish interested enough to strike? I went back over area a few times with no more strikes.
I have not had any problems catching larger crappie until today. Weather conditions change, wind...temp..I'm assuming these are all factors I should be aware.
And where were all the larger crappie? I search the lake for them. It's a shallow lake with deepest part I could find at 7 ft ...mainly 5 ft in depth.
Just curious since new to crappie fishing.
thanks.

The larger crappie have probably moved shallower for the spawn. Try a different area.