Well, I'm sorry if you misunderstood what I said, but you did ask for my opinion.
I do love
Ophelia, both on its own and as part of sibsets. I do understand that
Malcolm and
Scarlett are already named and are your children, so you cannot change that.
However, I will phrase my answer a different way:
Ophelia and
Scarlett both feel like strong, dramatic, almost theatrical names to me. I was not aware of the Shakespeare connection of Malcolm-I have read only a few of his plays. Anyway,
Ophelia and
Scarlett, combined with
Malcolm, feels unbalanced to me-Malcolm feels solid, not dramatic, to me. Therefore, if an
Ophelia was added to the mix, your
Malcolm may feel like the odd man out. Again, just IMO.
Happy decision making.