I would guess that you have two male dragons who have recently reached maturity and are fighting over territory/hierarchy. Males especially will continue to fight until they establish dominance for the best basking sight, most food etc. Once this is established, you may need to provide a basking spot and food source for the non-dominant lizard, depending on how strong the dominance is. Fighting may continue even once dominance is established and serious damage can be done to the dragons during this process. Larger enclosures (3-4 feet) and in some case complete separation is the only way to solve this issue.