I think you rely on lines a tad too much (like in that one of the rose). What I would do is draw the lineart really lightly and then block in all the shading. After that, do a colour wash of the base colours (or maybe block in the base colours first, let it dry and then do the shading if you're less confident). That should make your shading more crisp. I think watercolours are all about crispyness. Your work looks a bit brushy and it seems that you rely alot on hatching, I personally don't really like hatching with paints because it doesn't make it look realistic. If you're aiming for something that's a little more impressionist, I've got no problem with that. I just find it helpful knowing how to shade in many different ways.
When you do the background (like that red one with the horse), do a wash in the background with clean water and then brush in the colours. It'll make the colours more uniform and appear less brushy. I also find using tissues helps create some nice effects. Maybe you should experiment more with tissues.
Are you using one of them watercolour pads where you put water on it to dissolve the paint? I actually find that the colour quality's not as good when you're using those, I suggest using gauche or them watercolours your get in tubes ;D
I'm not an expert on watercolour but I like to play with it a bit. I find my skills in oil painting useful for watercolours. I find just playing with tools a good way to learn because I'm too cheap to get books or lessons (anyways, it's not like Brunei's an arty country) xD