I've finally got a good feel for the game and have moved off of the easy setting. When moving to the medium I have occured an issue with the AI, what I feel may be an issue, probably something I am doing.

Normally I get a lot of "dead planets" around my starting location that still have the crsytal and metal extractors. I will take ownership of them, works great for me. I get a lot of resources quickly, can get a lot of tech and ships quickly. The problem I have is the other 3 ai players will horde all of their fleets in the closest "dead planet" and I have to match all of their military combined with ships and capitals to keep them from attacking. So this prevents me from advancing since all of my fleet has to go to this one planet in order to prevent all of the ai of attacking at once. When I try to attack them, when I have a large enough fleet, as soon as I phase jump to them, they all phase jump to the planet I just left. This happens everytime pretty much. Is there something I am doing wrong?

edit: also to note, they don't attack each other in this system.