A 2ft Cube tank is only big enough for very young Discus.
They need to be in a group of 5 or more until they are about 4" at the very least which would overstock your tank, plus you would need a bigger tank once they grow. A small tank has other problems too, the water is more likely to fluctuate in quality quicker than a large tank and with Discus, you need water to be stable all the time to keep healthy Discus.
If you can afford it, buy a bigger tank and invest in an oversized filter and either a de-ioniser or RO unit to get the best water quality. Young Discus need water that isnt TOO soft while they are growing, while older are happier in soft water but can be acclimatised to the harder stuff.
If you are willing to put in the money and time needed to keep Discus, you will find they are no harder to keep than any other fish once settled in, and will pay you back many times over with their charming behaviour and friendliness.
Be aware though, these arent really community fish and are best kept with a few select species of fish, so if you like a lot of constant activity in the tank, Discus arent the best choice.
Im preparing my tank which is 47g for Discus in the next few months after not having kept them for over two years.. (its important to have a tank stabilised well in advance of getting them) and will let you know how it goes, in the mean time, read as much as you can on them and check every piece of information with at least two different sources as there are people who love to keep Discus mysterious and pretend they are charmed when it comes to keeping and breeding them.
I promise you will be hooked by the time it comes to actually buying them!!
Ken