Goji Berry, Leaves turning white

Just wondered if anyone could shed some light on this problem, I have a Goji Berry and all the large leaves turned white and dropped off, I could rub the leaves and rub it off but I left them to go white and eventually they all dropped off and new leaves came and then it happened again, I have given the plant a really large pot which I will leave it in for good, some leaves still look a bit white but is now flowering, was it too much water? too small a pot? Was it leaf mould and what are the most common causes?

Looking foward to some superfruit!.

Looking forward to your answers also:thumb:

 

Thanks MF for replying, I had a look at it yesterday and its gone back to looking healthy..for now!.

Thanks for the links, It says to change some of the soil each year, A neighbour works with a company that takes turkey manure from local farms (this is bootifull Naarfolk:lollol, I can have some if i need it, would it work if i dug a litle in with some new soil next year?