in combat mana stops recharging after turn 25 or so?

[rena]

I was fighting the final tournament battle (im only level 20 so i was getting slaughtered but was getting through it slowly) and at around turn 25 my 4 mana a turn stopped coming i was stucj at one rage and 1 mana for the rest of the fight which i lost and could have won if it had kept recharging. Is this intentional and if so it needs to be in the ability description thanks.