Mesh problem (weird shadow on objects) {Solved}

As you can see, normal objects with a flat surface have no weird shadow on top of them. My objects have a shadow and I can't figure out why.. I know how to convert meshes (I converted the table on the left) and those meshes always look normal. So what am I doing wrong? The texture file of the right painting is completely white.. I can't imagine that it's a texture problem. I also don't think that it's a specular or bump problem, but who knows..

I uploaded the .blend file of my painting (on the right) here in case you need it: drive.google.com/open?id=0B1M5B-shdZkCckpWVEtCb2ptUWM

Help is highly appreciated


I just found the solution  (http://sims4studio.com/thread/7368/shadow-issue-resized-recolored-flowers?page=1&scrollTo=66040)
Thank you orangemittens!