Got the file but it contains an item I don't have "date_palm_3.veg". I will replace it by some other palm.

But... when I opened the file the first thing I noticed was that you have a very big light panel behind the camera to provide ambient light. I would say that's not a good idea. I made some tests with light panels some months ago and found out that they easily create blotches in the shadows (and, if I'm not mistaken, it also increases render times considerably). I would strongly recommend to delete the light panel. Vue has two better tools (IMO) to do just what you are trying to achieve with the light panel. You can increase the sky dome lighting gain (my recommendation) or create a dark blue directional light.

I will do some tests tomorrow because it's 3 a.m. here and I have to get some sleep...