i had the same problem and just raised the thermostat to 104 and now the tubs are at 90-92 in the back..the front were 70 to 74 so i put light fictures in the front on dimmers and now they are where i want them to be at around 80..just have to raise or lower the dimmer once in a while..buy the way red bulbs..my house drops to 68-70 at night and 70-74 during the day..