Something odd regarding fireball crit... help

Hi all i've a problem i cant understand..

my equip il all the way crit i haev 28% crit rate and 34% fire crit rate im using "recount" to keep tracking of crit

all my fire spell seems to crit fine except for fireball that crito not over 7% ... is there something i miss ? cant understand why such a low crit rate only on fireball...

thanks for help ^^