My response:

Without watching them we don’t know if it’s dominance or jealousy. In multi bird, cages, it’s best to place multiple food and water dishes, also separate sleeping perches.

Then create “safe zones” from enrichment toys or even Romain lettuce clipped to the cage walls so any bird can get privacy when needed.

Yeah like you never wanted to crawl into bed and be left alone.

My guess your cage has few toys or accessories so your birds have nothing to do except pick at each other.

10 budgies, 4 years, no eggs, no fights.

(10 budgie aviary)

Lastly, introduce lighting over the cage top with a timer.

Full Spectrum Economy Daylight Bulb with Clamp Light & Timer