Welcome to a long and winding path. Lighting and photography are like a hand in a well fitting glove. There is a great book you need to get and read called: "Light: Science and Magic" by Fil Hunter, Steven Biver and Paul Fuqua. It's a great read and even has some "assignments" in it for you to try.
As stated above, you might try a different set up with the posterboards, but you might also try moving the lights either closer on one side of farther away on one side to help give a "Key" and "Fill" type of lighting. Thus creating some shadows. Don't be afraid of shadows, they create depth and character in an image.
As you mature with your photogragraphic lighting you may want to move up to using flash instead of constant type lights. And then getting that flash off the camera and having it triggered either through a PC cord or a wireless trigger of some sort. Then things start to get real fun!
Here's a shot taken recently using nothing but a shaft of light coming through a greenhouse window.
Natural light and a fast lens
On Camera flash, but the power was turned way, way down. More fill than anything.
A single flash unit off camera and directly above the flower. This was a tough one: Hand held 1/60 @ f22 shot at 63mm focal range and using a 12mm extension tube behind my 24-70 f2.8L lens. Flash was mounted to a macro style flash bracket. So the whole camera assembly wieghed in at around 8 to 10 lbs.
And finally Off Camera Flash using wireless triggers and multiple flash units.
here's the set up shot for that last image just to show you what I did to create that image.
You can see that the main light is only coming from one side and that the other side has a white foamcore bounce card. The back light was in fact the background as well. It's a 2'X2' Softbox placed right behind the orchid. The size and proximity of the shoot-throu umbrella craets a huge source and give a lot of soft, wrap around light. But without the bouce board it was a touch too dark of the right side of the image. I played with that by moving it in and out until I found a placement I liked.
Hopefully that helps some.
Also, one tip: Shoot tighter! The orchid is beautiful, the pot isn't. If you don't have a lens that will allow you to get closer or crop out the parts of the scene that aren't helping, get a set of Kenko Extension Tubes from an eBay seller ($160 for a set of three) and move in closer to your blooms! I love mine and I used them in all the images except the wide set-up shot above.
Keep shooting, you'll only get better with shutter releases.