I don't want to be disrespectful or ignite any flame but it all sounds strange to me.
Maybe you are talking about some particular and rare case?
The rule is that it integrates all the B group together, taking only single vitamins of the B group could lead to dangerous imbalances over time.
Vitamin B6 toxicity?
It only happens with 500 mg per day for a long time, this is a very high dose!
The strongest (high-dose) B Complex I take provides only 10 mg of vitamin B6 (the minimum recommended dose for adults fluctuates is 1.3 mg and goes up to 1.7 mg daily if you are over 50)
Vitamin B6 can be taken individually in high doses to treat specific diseases but when this occurs it is by * indication of a doctor * who makes sure that certain limits are not exceeded.
Nobody will go to the hospital if they take a common "B Complex" supplement and follow the directions on the package.
Note: Bananas are rich in B6, three or four large bananas will give you your daily B6