Cory randomly dieing?

Question
Hello!  First off I'll list the conditions of my tank.  I cleaned my 10 gallon tank a couple days ago and inside the tank I have 3 corys, 4 neons, 3 guppies, 2 loaches(temporary), several shrimp and a ton of snails (which make a tasty snack for the loaches :)  Anyways I just did a full chemical test and everything is looking just fine.  All my fish have been acting normal except for my albino cory which I got about a month or two ago.  Last night I noticed a decrease in his activity and the next morning he was dead.  Now I don't know if it was the quality of the fish or something might have entered my tank.  I wouldn't be surprised if his general health was just poor to begin with becuase it was from Petsmart (I don't know their repuatation on fish selling).  But other fish sellers have told me to watch out for large fish stores like them or Petcetera becuase they don't take care of their fish as much.  Anyways I wanted to know if it was just my albino cory's bad health or if him magically dieing is forshadowing an even larger epidemic to come.  I want to nip this problem in the bum before it gets any worse.

Answer
I appreciate you giving me the basic info and wanting to make sure something bigger does not develop. First, it may be possible that the loaches or even the shrimp did something to the cory. While the shrimp would not be my first suspicion, sometimes they can be surprisingly aggressive. Also, I know you say the loaches are temp in the 10 gallon but they tend to get aggressive if kept in small tank and a 10 gallon is pretty small for a loach that can get very big. I would first suspect another fish in the tank picking on the dead cory, watch them closely to make sure there is not any bullies going around trying ot take over for a few days. Next, I would look at the condition of all the other fish, do any of them have signs of disease or parasites like not eating, not swimming, swimming bad, bumps, fuzzy spots, spots like salt, velvet spots or any other odd symptoms? If not, I would not worry too much about the cause being a disease or parasite. However, keep a close eye out or a week or so, just to make sure something does not develop. If you catch it soon chances are high that it should not be a problem but do not treat unless you know for sure you have a disease or parasite problem. Other than these two idea, yes, it is very likely that the fish was not healthy to begin with. The main chain stores do not care for thier fish properly. The other fish sellers are right on, the chain stores do not put much effort into making sure their customers get healthy fish. I would advise you to never buy fish from large chain stores again in the future unless you have no other possible way to get fish. If you have to purchase fish at large chain stores, you must watch them closely before you buy any. Never buy a fish from a tank with a dead fish in it. Make sure the fish are acting normal and active. Just take time to pick out the one you want and make sure it looks the best possible. But again, avoid buying fish from these chain stores. Other than a bully, disease/parasite, or just poor health, I would only next guess lack of food. It sounds like the bottom of your tank is quite full, sometimes the runts tend to not get enough food. The shrimp are aggressive eaters, as are the loaches, and even the corys. Combine these all together and any runts of the litter will have hard time getting anything. However, do let this make you overfeed just make sure all the fish get something without adding excess food on the gravel. As of now, unless there are other symptoms present on the other fish, I would not give much thought to the death. Albino corys are some of my favs and are super fun to watch so hopefully you will be able to replace him. Otherwise, just keep a close eye on them for a week or so just to be sure and continue to give your fish wonderful care. I hope this has helped. Let me know if you need any more help or have more questions.