You won't think it such a good price if they now die on you!
The 6 danios on their own would have been best but it is too late now so lets see what we can do to get the fish over this without too much stress and death.
The bristlenoses are often referred to as plecostomus but are, in fact, Ancistrus sp. They will have nothing to browse on in a new tank so make sure they get the bottom dweller pellets to eat (same goes for the corys). The ancistrus also appreciate wood in their diet to aid digestion so it would be helpful if you have some driftwood in there. I think though that good quality bottom dweller pellets have wood in them for this purpose.
The rainbow shark is too big for your tank. It grows up to 15cm and needs room to swim. Please return it. If you insist on keeping it, and it survives, it is omnivorous and likes a vegetable component in its diet, like spirulina. It may also get aggressive and territorial as it ages, especially in a tank the size of yours.
The Nitra-Zorb will probably stuff up your test readings so you won't have a true idea of ammonia levels. The water changes you plan to do will be good and you will need to keep them up until the tank has cycled. The Nitra-Zorb may slow down the process.
Temperature will vary (try seeing what it is in the middle of the night when the room temperature has dropped a lot) and your variation is nothing to worry about. Anything between 24 - 27 is fine. Most keep their tanks around 26C.
Do not add any more fish until your tank has fully cycled - at least 1 month.