Cory Cat Spinning Like Torpedo

[nic1]

Hi,
I came on yesterday and saw that he had died, aw sorry to hear that
The only reason why I asked about the frog was because they need to be able to get to the surface easily for air and if the tank was too deep or if there weren't any places for him to sit near the surface then he could of died that way. They aren't the best swimmers and although the frozen blood worm is part if his dietary requirements he still would of needed more as a whole.
I think the frog and cory deaths were un related, but he could of played a part. As the frogs of that kind aren't great waste producers their food is, this uneaten food could of been left in the bottom of the tank whilst you was away polluting it up, getting into the gravel etc, the cory came along and being a bottom dweller could of slowly been poisoned to the point where he couldn't fight off infection as his immune system was comprimised and any parasite he did have previously just took over.
If you're still worried about adding anymore fish at this point, I would hold off for 4 weeks and keep an eye on the gourami, like star4 said - clean the substrate really well when you do the weekly cleans, and look for any signs of infection. If alls good then add more
Corys like sand to dig around in and the like their own company, they have a totally different personality when you have them in odd group numbers.

 

[star4]

Good news the gourami looks fine . Nic1 has already explained about uneaten food and why the cory got sick - which is what I also suspect is the problem.
 
Again ditto nic's advice, I wouldnt add more fish just at this moment, if there is a bacterial problem new fish with lower immune systems (lowered from the stress of being in a shop, transportation, bagging etc) would be at risk.
 
Being as the gourami looks fine, I take by now you would have already done a gravel vac and water change, but instead of daily for a week, do one every other day, for a week then 3 days and so on, gravel vac each time.