Okay here are new updates on my quarantined gramm. More leaves are discoloring and looking worse. I had to order the physan and it is on its way. It is in a shady breezy part of the back porch. It gets bright partial early and late evening sun. And has been watered about3-5 days when medium is appearing to be dry when I insert a skewer.
I'm sorry your new baby is not doing so well:-( Really do not have any advise, I am not experienced with these things:-( It seems like the seller for your 2 plants sent you some not so good ones!
The other I have seems to be happy and healthy. This one even has new phulb shoots. Thats what I cant seem to figure out. The roots are healthy 2. I soaked it in seaweed extract today w water etc.... maybe if the leaves all fall off it will perk back up or maybe it is shock...
I do not grow these, but if that spot is spreading I would cut it off the infected part of the leaf. Hopefully, someone who grows these will be able to give you more insight.