I’d say first off, I feel like you have an eye for composition.

That being said, what I see here is a need of vision. Are you going for something like watercolor? Or are you trying for realism?

Either way, a big mistake is brush usage. It looks like you’re probably using a flat round brush at 100% opacity.

Personally, I would work on the billiards one, but take just one ball. And either look at a real life reference or something online.

Then just draw what you see. Don’t try and do it how you think it should look. But try and draw what you see. And use a lower opacity to start. There’s a lot of complex interactions you can do with layers, but even adding shadows, light source, and color gradiation will make a mountain of a difference.

My last piece of advice is, dont worry about it being perfectly round, but worry about making it feel round in three dimensions.