Massive loss of fighters - please help!!!

[Jason2]

I am currently playing a game in a large, cluster universe with not all warp points connected - so I am moving cluster to cluster.

I started everyone at medium tech and the Computer on High/High (difficulty/bonus).

I had a fleet with 6 Carriers each carrying 79 large fighters and attacked a large planet owned by the Sergetti (non-mod). I usually play on Strategic since tactical would take too long. I had just finished wiping out a system of Sergetti and had the blueprints of the large weapon and medium weapons platforms - each only had 1 point defense cannon. Yet, all 474 of my large fighters were wiped out in about 3 minutes! Assume whatever weapons you want - what could do this so quickly to so many fighters??

Help!!!