Spend every resource you can on those planets, and do it NOW. No point letting him steal even more from you. I really really should have brought a main battle fleet to the core earlier then now. From what I can see he is making masses and masses of 1 scout fleets. Building destroyer fleets as powerful as you can should help kill them.
Cheers, did that last night before I went to bed. Built as much as I can on all my planets and sent them towards the main, with a handful sent elsewhere to stop his expansion (he has a few planets I want, so no long-run harm
). I had a few small fleets orbiting and had them head there too. Hopefully everything combined will be enough to take it and hold it until next weekend
EDIT: Lots of single scout fleets are very effective at taking inactive players btw. They have a 4.5% chance at capitulation, so lots of them can increase your chances quite significantly (yes, we have been over the maths before, no, I don't remember if what I just said is correct
)