What is supposed to happen: you get an elemental damage boost that gradually fades at different rates for each damage type. It does fade as intended, but the buggy portion is this:

each round the spells lasts ADDS a permanent +1 fire damage, which  accumulates.

very odd. The spell has no requirements for testing purposes. The additional test of this spell wsa to check if seperate spell elements could have different durations, and observing the particle effects from round to round.