Plants will grow fine in sand. You may need to add some liquid fertilizer. Slow-growing plants like the Anubias and Java Fern may be fine with just the nutrients from water changes and fgish feeding, but other plants might need a supplement. A complete liquid is usually sufficient, we can discuss brands if asked.
To the corys. I will never buy any cory species that has not been in the fish store for at least one week, often two. Corys are extremely sensitive fish to ammonia, and on top of this they do not travel well. I have had stores tell me of receiving bags of dead corys. They are easily stressed out just by being netted. If the stress of all this is severe enough, they will even release a toxin from the base of the pectoral spine that kills themselves and other fish in the confines of a bag. That is not what happened here, as this toxin is a white milky fluid and its effect is immediate. But it shows how sensitive they can be.
Second, on the acclimating at home. Never add the bag water to your aquarium, even if it is a quarantine. There are likely all sorts of pathogens in the water, plus high ammonia, and you do not want any of this in your tanks. Add the tank water to the bag, or do this in a pail by the drip method as someone else mentioned, and net the fish into the tank. There is some difference of opinion as to what benefit if any acclimation has on fish. I know of a local catfish importer who only equalizes the temperature, nothing more. But I have always mixed the waters in the bag for a period of time (depends upon species) and so far have had no issues I can pinpoint to the acclimation.
Byron.
I'll see what I can do. 
