[3V4JKZ2]

I am playing a game as Hinnom, and currently at war with Lanka.

My Astral Ba'aal's have twice been set up:

Power of the Spheres --- +1 path, 1 gem.
Solar Brilliance --- S5, requires 5 gems.

With 6-8 gems.

With Power of the Spheres, they go to 4. That means they should be able to cast solar brilliance with an extra gem. They don't. The enemy casts darkness, and is full of demons and undead. I have no demons and no undead, and fight better in light. Solar Brilliance doesn't get cast. Why not?