I have found the growth in red leafed plants slower than typicals/green leaves. Look ok to me. My red plants grow smaller than my others, possibly they need far more light/sun than even outdoors in England can give ?
That looks like a Maroon Monster. I have one as well (a starter size) and yes that growth is identical to what mine shows. I will tell you of all the red colored VFTs the Maroon Monster is the most vigorous in my experience. It grows faster than either Royal Red or Akai Ryu.