I asked a question on authenticity in an earlier thread and i think it is a reasonable assumption that it is very difficult to prove once and for all the authenticity of a teapot.
Pardon me, but is the teapot maker Mr Hua Jian Min a famous potter? If so, you might like to google and compare the craftsmanship online and in other shops. It might give you a better basis to make a judgment.
Did you buy them online or through ebay? No offence intended to any businessmen here, i do think you need to get from trusted dealers. I came across this website deeho and they have some wonderful teapots. If you have any experience with them, do share as i intend to get one from them in the near future.
Some of the bigger teapot sellers may bring in yixing artists on a regular basis. If so, you might like to buy their works. At least you will be assured that these were indeed made by the potter. This appears to be a safer bet than online purchases as you also get to test out the teapots. I doubt that there is any warranty once the teapot passes into your hands.