Wow thanks for this... So I need to markedly increase my contrast when I pick my colors

Other pointers:

Contrast is your friend. Your two lightest colors are barely different. Either scrap one or make their value further apart. 

Clouds are physical objects they cast shadows too.

A small palette change makes it into a completely different pic:

https://sta.sh/01uq8vyajxsx

Thanks I tried to reflect the changes in a 4th tower with clouds and caves.  imgur.com/wYcQKaf

Hey. Some pointers since you asked for them:

1) Clouds are objects too. They need to show light direction just like the tower/mountain itself. (usually clouds are dark on the bottom and bright on the top)

2) Cave entrances rarely have a bottom edge to highlight. Just let the bottom fade into the dark. And the entrance itself usually isn't lit from the front. (see below:)

3) Listen to Bob Ross. Every shadow has a corresponding highlight somewhere. If you have a crack in the tower, one part casts shadow, but the other part should be highlighted.

Keep at it. I think landscapes might be your thing!