It's best to preheat your air fryer first to ensure food is cooked evenly and at the desired level of crispiness. Also, make sure the vegetables are tossed in a little oil and arranged in a single layer in the air fryer. Lastly, you may need to cook the vegetables in the air fryer for another minute or two if you want the edges browner. Just make sure to keep a close eye to avoid overcooking.