I have tattoos on all my upper and lower sections of my fingers,and finger tattoos just suck ,and they ALWAYS need a touch up and maybe a second touch up,
and they ALWAYS can blow out a little,small parts of the finger tattoo can fall out too,if there is any scar tissue on fingers(like i have from small cuts over the years) can cause trouble too.
IMO it looks like that's what happened,similar happened to me and a touch up helped a lot.
it is what it is.