Watercolor Clouds

So I decided to take on a challenge that has always eluded me...clouds. I love watching clouds moving through the sky, whether it's high wispy cirrus clouds or big cotton ball like cumulus clouds...I could watch them  all day, but when it comes to painting them...that's when I struggle.

My inspiration for this piece was a watercolor piece by Charles Cherry titled "Distant Hills and Clouds".
When I started to paint this, I thought I would go outside to be inspired, but there wasn't a cloud in the sky. I also noticed that I had no palette to mix colors on. I haven't worked plein air in quite a while so some of my supplies we're sitting on my table at home. I ended up pulling the color right from the tube. I hate doing it for fear I'll contaminate the whole tube, but as you can see, I only used 3 colors total and only mixed colors a little on the paper.
Looking at the finished piece, I needed to use a darker color in the clouds for the shadows. I also need to loosen up my "cloud shape". It looks too uniform and too scalloped. It does not come across as realistic.  Any pointers would be appreciated.