try upping your stat , but continue to monitor your thermometer .I've got a heat mat and i've set it to 32 degrees C and it seems to be struggling to get it to this temperature,
a ahs is a well kinda mini heater they come in different wattage for different size viv's and have a thermostat on the end of a cable on the actual unit is a dial that you set to temp you put the theromstat half way across the viv and it cuts out when the temp you set is reached.My heat mat is inside the viv but under a substrate.
I havn't thought about using a... Ahs? I don't even know what it is!? Lol Sorry.
But they are better? I might look into it.