Beautiful painting! I especially love the trees and lighting in the background! Two crits: 1) The grass appears a bit too green for the lighting, especially compared to how the leaves appear. 2) The background seems more realized than the foreground. Perhaps some more details to the river in the foreground (esp the bank) and something additional on the left would make it even better.
I am not being mean. I'd just like to share my opinion of the things you've pointed out. 1. It does say 'mystic forest' I think the verdant grass add to this ideal greatly. 2. I think the background draws the eye ahead and since there is really nothing of importance in the foreground there really isn't a reason to be bent up over lack of sharp detail there.
Not saying it's without its flaws but this piece pays attention to lighting and the calmness of the water so I would give slack in those areas.