Give each player/enemy an instance variable for each type of status effect. Run them as Type Number - since you plan to have levels of each type - instead of as booleans. If defenseBreak = 1 defense=defense*0.6 // If defenseBreak = 2 defense=defense *0.45.
Depending how your game works you would want a minimal of 3 checks
- Before attacks to check if effects stop you from attacking or effects effect who you should target. (Ex. if you're asleep you don't get a turn, if 1 of 2 enemies is asleep you hit the awake one -assuming auto fighting).
- When getting hit - for any effects that change damage - defense break
- Damage check/Effect drop - End of each Turn type of thing - or if real time then every x seconds to tick off things such as poison or buffs timer ending