You won't be able to invest into Fire Attack, stamina would be the option if it used that for the fire attack otherwise there's nothing to put in for a Fire Steed other then hit points, resists and damage but the resists and damage for a second gen should be maxed.
So you'll have a lot of points left to spend once you hit the max hit points.
Unless this pet is over level 30 then Fire Attack might open up, not sure though.
