Good morning all!!

So my I got my 2 v221 tanks on Wed. My thermostat (Herpstat 4) arrived on Friday.

i have both tanks set-up with the Heat panels mounted in the same location (upper right corner of tank).

The tanks are stacked on top of one another and I put the probes directly under the heat panel above the substrate.

I have the thermostat set to 90° proportional...

The tank on top is reading perfectly at 90° while the tank on the bottom is having a hard time getting to 90° ..... The heat panel has been working at a hundred percent for a few days now and I can't get the temperature any higher than 87 on the bottom tank.

Anybody have any suggestions or thoughts as to why this is happening?