Pests aside - your best bet for those might be to pull all the rocks and leave them in the sun for a few days. There are things that eat the problems you have, but if you're having trouble keeping things alive, we might not want to go there. Before going too far...
I think there's some value in keeping it running for a while to try and learn what is wrong to avoid the same mistake when you start it up again.
Full set of tank parameters, size/volume, lighting, maintenance routine and every test number you can get will be a good start.