Question about soft shell

[hpfirework]

My first tortoise is a 4 month old Greek. I just found out, the top of the shell is a little soft, and the color is a little lighter than the rest part. I did not notice until I pressed the shell a little harder with finger nail. It's like wood, not stone hard, you feel you could make a mark on it with nail tip. Is this an early sign of shell rot, or calcium deficiency?

 

[Yvonne G]

Normally its the plastron that shows the first signs of calcium deficiency. Can you show us a picture of the spot?