Your aperture is f22 for no reason, you don't need a lot of DoF. Your Tamron 28-75/2.8, which I've had for years and is my most used, like most lenses, is sharpest at f8. If you are using flash and light bulbs on your box, let more ambient background light in with a slower shutter. Shutter speed doesn't matter for flash. I'm assuming your using a tripod. Also, the 2sec delay does Mirror Lockup to reduce vibrations.
Minimum focus on the Tamron lens is 12" so I'm not sure why you are at 75mm. I don't do product shots but here is a recent shot with that lens at f8 & 43 mm with diffused flash and a longer exposure to balance the ambient light. I had a black cloth behind the blossom.
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