I have a hot spot re model spa and had just refilled it after the winter, it was running fine and the water temperature was perfect. Then the spa began to leak through the heater block where the power wires come out from. I drained the spa to the bottom jets and the leak stopped. Is it my heater element or is there some gasket or o-rings that neeed to be replaced.

On this particular Hot Spot, if there are mounting nuts that attach the heater element to the outside of the stainless heater case, then you should be able to remove the element and inspect / replace them as necessary.

However, on those that I've seen, the heater element is welded to the case. In this situation, you'll need to replace the heater assembly completely.