I don’t think thickness of the glass is a problem.
Really like the fact that it’s a slim sheet of glas and you still can see the floor through the glass !
But they lack a little bit of detail. Now it look likes the (concrete) of the walls is making some weird turns on the sides just to fit a window. The fact that that the framing between the glass portions also has a concrete or stucco look makes it look strange and not realistic.
A while ago i tried it myself (in this topic)
Please ignore the shadows 
Maybe the weird looking corners in the wall are not necesary?
Just by giving the mullions another colour it gives a more realistic feeling. In reality a wall in a window always has a frame around it.
Except a fully glazed curtain wall, but that’s a different story…