I actually started in Xi'an. Took the 3 turns it takes to move from Beijing to Xi'an before started. However Beijing was the first city I built and it was far superior to Xi'an in production and food.
My 3rd city was Nanjing, followed by Ghangzhou, followed by Korea, followed by Hangzhou, followed by Bactou (or something like that) followed by one in between Korea and Beijing, followed by one in Mongolia (Which was eventually razed by Barbs)
My solution to the problem. Well first I am think I will remove some of the forests to see if the lack of chopping ability will weaken China.
However its 2 am and I have school tomorrow, so I will try that tomrrow when I get home
I highly suspect that the problem is limited to marathon; because even the Ai was able to found both Toaism and Confucianism in 3000 ad On both of my tests; please try normal speed next time because it is near impossible/extremely difficul to balance all three speeds.
If the problem persists ill change the terrain but there is no way for me to change the marathon modifiers unfortunately; maybe Leoreth can help us