Probably a relatively simple problem to fix, but it seems the Wisdom Wood Slabs and Wisdom Wood Stairs have strange lighting rendering. I believe they are counting as a full block, as the inner corners of stairs and bottom half of top-slabs against any block causes an excessively dark patch to form, even worse than Vanilla slabs and stairs.

Granted, this is a very minor gripe, but quite noticable when building with Wisdom Wood.
Note: I am using Optifine, although I do not get this issue with any other stairs or slabs from any mod I have installed, so I am pretty sure it's on your end.

same here: https://www.dropbox.com/s/u4zz75qa5c1xggi/Captura%20de%20tela%202018-12-02%2019.46.28.png?dl=0