firehawkclone

I just bought this house 4 months ago and it has a pebble tech(spelling?) inground pool and spa. Well the spa has been loosing about 2 to 3" of water every day or two the last 5 days. The only change I have done is to turn on the propane heater to 70deg to take the bite out of the water. Could the heater be doing this or do I hacve a leak? Thank you(newbe) John