possibilities based on my experience: heat, humidity, UV light, age
But due to my inexperience I need you.

Specifics of circumstances:
I recently shot with some Provia 100 (4x5). They were stored in the film holder for over 6 months in a hot humid environment. After I shot it (they are correctly exposed), and developed, some have a greenish yellow tinge. Much like it was shot with an florescent light. Disclosure: Florescent light is not the cause. One sheet out of the set turned out fine. Secondly, I was using multiple day-light balanced strobes. Flourcent lighting cannot be the cause.

- should I store film short term (i.e. 3-12 months) in the fridge. And longer in the freezer. (Which I already do)
- Should i store the film in a light tight box to block UV light?
- is film in film boxes or film holders susceptible to uv light? And might fog?
- Should I store the film in a humidity controlled environment (local humidity is quite humid; typically 85% or more)?
- do I need to keep all film away from direct sunlight (i.e. in a dark cupboard or closet?)
- All of the above?