What's the height of the truck receiver? The ball typically sits a couple inches above the receiver tube.
Are you sure the trailer is 24" when the trailer is level?
Yes, you want the trailer pretty close to level going down the road but make sure you have an issue before doing something.
- Use a weight distributing hitch (WDH). This will reduce how much the truck squats when loaded. If it's still squatting a lot, there are suspension upgrades that can reduce it more.
- Most WDH can be adjusted to raise the ball 3-4 inches.
Those are the simple straight forward solutions.
You could check if you can fit slightly larger diameter tires without other complications. This could buy you an inch or two but it will throw off your speedometer and if too large, could lug your engine as you are effectively in a higher gear.
Then there are lift kits (think off road trucks) but they aren't always well suited to towing.
A decent welder should be able to put on a new trailer hitch that drops the connection a few inches.
If the trailer springs are above the axle, you can do a flip and put them below.