Monte Carlo Patches W/ Leaves Turning Translucent And Melting Towards The Substrate

Heya all, long time forum lurker here. Most of the things that I've done in my tank have come from information that I've learned here. I thought I'll jump in and join the community finally and engage . Would really appreciate the help. Also please let me know if this is not the right place to post this.

I have this 9-month-old 55g and have recently gone down the co2 inject route (currently at ~2.5bps). I'm also dosing Seachem Potassium, Iron, Flourish and Excel following the seachem dosing guide.


Noticed 2 days ago, that I have this patch of Monte Carlo turning translucent from the top new growth and appears to be punching a hole down towards the substrate. Today, I noticed a new patch of this come up just a couple of centimetres close to the original patch. It is worrying that it's happening at such a fast rate.

Is this some sort of disease or deficiency? I have runners growing on the edges and it looks healthy to me apart from this.