A lot fo Nirvana gear is F2s (knockoffs, if you must be technical lol)... Variation is to be expected; you should know what you are looking for in a given pack, and follow the correct procedure for choosing and propagating an exceptional mother.
I buy Nirvana seeds and grow them out, saving the best female for a clone mother, and if you want to back up your seed collection, choose the female that best represents what the strain is SUPPOSED to be, and pollinate a clone of her with the most healthy, vigorous male, and enjoy your genetics!