Hi,

This may be a daft idea so feel free to ignore it but, over here, some brands of heatpads get hotter on one side and if your top one is doing the same that might explain it.

Or possibly try putting a layer of insulator between the bottom tub and the heatpad for the top? Reflectix (I think) was one type that was mentioned as being moderately priced enough you could possibly test this with no major outlay.

Not sure if any of that made sense (it's 7 am and I'm a lil punchy) so you may need some kind soul to decode.


dr del