If you are using the flash as fill, which may be the case, then the white balance is a mix of the flash and ambient light. If you use the "warm cards" to set your white balance, then that takes into account both the flash and the ambient since you fill the frame with the card and shoot it as your WB reference shot. If you use just a white card then you are getting a WB that will make a gray card look 18% gray. You can often just set the Kelvin setting of the camera (if your camera lets you do that) to 5800K and that warms up the image quite a bit. If you shoot RAW, then you can adjust the color balance in post processing to anything you want.
I use a Black/Gray/White target that was made by Ed Pierce and is now licensed to Wescott. You can use the back side for white balance, you you can just use the middle gray area of the card also if you fill the center of the camera with it. You can use your camera's histogram and the BGW target to zero in on the exposure.