I've had this old boy for about 20 years now. I noticed a white spot on his shell about a month ago but last week I left and when I came back I noticed this redness around it. I am really worried because he's been chill, happy, and healthy for all of his life. Just fed him and let him do his thing. Is this the start of shell rot? I can go and get medicine at anytime I just want to make sure to get the right one. I've googled around and most shell rot pictures look very severe or different than this. Sorry in advance if this was answered before. Thanks.