How can I decrease the health of an item by 1?

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I am making a mine craft bed-wars mini-game designed for 1v1v1v1. In your base there is an item spawner that occasionally spawns iron and gold. To limit the amount that spawns I am going to use the nbt: Health. I am going to have a clock going into a command block that decreases the heath of all gold and iron by 1. They will eventually go from 5 to 0 and DE-spawn. I have this command started but I don't know what to put next.
/execute as @e[type=minecraft:item,nbt={Item:{id:"minecraft:gold_ingot",Count:1}}] run data merge entity @s {}
I just need something to make the health decrease.
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