The "pink_petals" item texture has a green pixel with a low opacity of 10 (on the grid it's positioned at "14, 5"). On Java the pixel doesn't appear however Bedrock doesn't support low opacity texture and render every single pixel that are more than 1 of opacity.
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Since MCPE-190209 was fixed in 1.21.70.25, this bug should be addressed as well. It has the exact same cause.
Can confirm that there's a transparent/stray pixel.
(On Bedrock) It's not so visible in the hotbar as it is in the player's hand/an item frame.