Pulling jigs hot then not

My brother the kids and I went to a little lake in Illinois early in June to pull curly tails.
We did what I think is pretty good catching 45 fish in 3.5 hrs, mostly crappie w a few gills. Nothing fancy just casting out jigs tipped w nibbles, trolling behind the boat.We go again 2 more times later in the month w very diff results. Only diff on last trips is I have longer poles to get baits further away from the boat and a feeling we will do good again based on the last trip. Each of the last 2 trips only about 20 fish w mainly gills and a couple crappie mixed in. I noticed a lot more baitfish the last 2 times out on the graph and right below the surface if the water. I was wondering if the amount of baitfish was a better option for the crappie than the jigs? Should I have switched to cranks. Lake is only 10 -15 feet deep w not a lot of contours. I know I can't expect for a homerun everytime but I can't help but think I could have done better w more knowledge . Any thought would be appreciated as I am pretty new to the whole trolling game

Trolling just under or though the shad, will work when they are feeding. Most of the summer crappie will lay deep in a shallow pond. The thermocline will tell you how deep they can be, but I catch most of my fish in 6-8' of water in a shallow lake. We fish a 177 acre lake that's only 10' deep an do ok during summer. Water temp 86 degrees on surface.

The more line you have out the deeper your baits will run.....
Lots of variables could have affected your bite but be sure between trips I'll match exactly what brought my bite until it don't work anymore.....

I’m thinkin a depth issue. Longer lines or a split shot, maybe the next heavier jig. Sometimes the bigger profile doesn’t work though. Could be slowing down a little might put the jigs right where they want them. Let us know when you figure them out.