On the topic of B6 - I started taking 50mg a day 2 cycles ago to increase LP which was about 11 days and got a BFP right away. Unfortunately that ended in chemical PG.
The following cycle I was taking Mega B as taking the B group vitamins together means they work better, also taking Vit D (which I was low in and it helps fertility) and Elevit.
I got a BFP again so no idea if it helped lengthen my LP as I never had a proper cycle since on it, but I really think it did help get me PG.
Currently only taking Elevit, just B6 50mg (mega B not rec'd during PG), Vit D and added fish oil.