I decided to start a new one!

I am using a prewired Ranco thermostat. For about a month now I've been using it with great success, temperatures only varied about 3*F.

However, I checked just now and one probes are telling me this.

Top: 90*F
Middle1: 86*F
Middle2: 90*F
Bottom: 95*F

What would cause those fluctuations from the thermostat? No storms or anything!

This morning they read:
Top: 91*F
Middle1: 86*F
Middle2: 91*F
Bottom: 95*F