Q.Peach tree fruit
Why are the peaches deformed and showing necrosis from the inside out? I am seeing small, black flying insects around the tree but no obvious signs of biting or fruit invasion. The peaches are beginning to ripen, but have additional “piggy-backed” peaches attached to the original peach. Can you tell me what the problem is and how to prevent this for next year’s crop? I pruned the tree back in February and also fertilized it with organic fertilizer. My tree is approximately 3-4 years old. Thank you for your time and assistance.

Your plant has began to reach the end of it's lifecycle.
If your plant produced a 'pup', it can be removed and potted.
https://www.gardeningknowhow.com/houseplants/bromeliad/growing-bromeliad-plants.htm