Quince Vranja

I planted a quince tree in 2014 but this year the leaves seem to be mostly yellow rather than green. Any idea what I can do?

I placed a willow paling three feet from the tree to prevent the wind blowing off the blossom but it does not block all the sunlight. The ground is rather waterlogged as when I take my rotary drier spike out, the water level is high in the ground tube.

thanks 

Marianne