Currently playing at genius level also. What turn were you at? Did the AI rush you en masse? What size galaxy? Number of opponents?

Turn drag appears related to increasing the number of citizens, after researching citizen recruitment techs. By turn 633 it's a real issue.

At war in and around turn 300, the AI enjoys building cities (as many as three on one planet) and garrisoning legions. They also deploy Core Detonation on invasions and fleets with one huge support ship and tons of tiny fighters.

For a challenge try the xenophobic trait - bonuses in research and penalties in military construction. 

luceo non uro