True Color Image and RGB bands

Hello everyone,
I am currently working with Level 2 products from Sentinel 2 and I wanted to create an RGB image with the bands B02, B03 and B04. Nonetheless, the results from the RGB channels taken from the True Color Image are very different in comparison to my assembled image. Maybe you can tell me why the assembled image made with the bands B02, B03 and B04 differs so much from the TCI. Is there an image processing step that has to be preceded before I can get the TCI.
Many thanks in advance.

maybe it is just a matter of contrast? Different colors for the same 1C scene (different dates)