You've got some nice textures in your Avocado, especially at the core.
About the body shadow , it confuses me that the body shadow of the front Avocado is at the right side, but of the back Avocado at the left side. Also the cast shadow goes to the right. That means the left side of the back Avocado should be lightened.
And the cast shadow is normally darker that the body shadow, as the body shadow gets reflected light from the ground, which also could result in some ground color in the body shadow area.
A good shadow colors is mostly a mixture of two dark complements (could be a perylene green with a dark red or what I use often an ultramarine blue with burnt siena) painted over the local color.
You should try and mix different complementary colors and see which mixes pleases you. To experiment with mixing the colors and learn which colors go well together and which not is very essential for water colors. And have fun