Bit swap

I bought a sweet iron D-Ring snaffle bit from horsefriendly.com. Vicki and I noticed that Sugar had a pronounced head toss when we rode her in Kentucky. What I've read about bits online leads me to believe the bit might be causing this. She needs something a little kinder than the Tom Thumb bit we bought in Kentucky. Not only because she is young, but because I am not the most experienced rider and I can unintentionally cause her pain. It wasn't very expensive so I don't have much to lose. We can move back to the Tom Thumb later if we need it for trail riding.