Urgent Care :: Shell rot under retained scutes?

[DogTheTurtle]

I have a 6 y.o. Red Eared Slider. For the first year, I had a basking area for it without any lamps (due to lack of research on my part) but subsequently, I added proper lamps and changed them regularly and it basked regularly for 4 years, however, despite this, it has never shed its scutes a single time. I tried supplementing its diet with Hikari wheat germ pellets and mixing a bunch of different pellets I read could help it to shed scutes but to no avail. Around 1 year ago, it suddenly stopped basking completely with no change in setup. Recently, it has started to eat much less than before, Ive seen slight red colourations in part of its shell, and it's last few faecal matter have been getting more black in colour (I suspect it contains blood). I've recently started to dry dock it but I am still very concerned for its wellbeing. Is there any way to tell if there is shell rot underneath the layers of retained scutes and is it normal for RES to have red colourations in the shell? I am afraid it has shell rot but I am unsure the signs such as a foul odour/ white patches/ soft shell are masked by the retained scutes.

Link to some photos of its shell: https://imgur.com/a/Q8BUgbP

[steve]

The not shedding may be due to overfeeding. I would guess there could be at least 2 different problems. First, the loose scutes that do not shed will trap water and debris causing infections that can go all the way through the shell. The second possibility is that such heavily retained scutes damage the healthier scutes underneath when there is physical movement (like being stuck on something).

I can't tell if there is any infection or shell rot from those pictures. The red coloration might come from water issues, but it's hard to tell what is going on past those retained scutes.

[DogTheTurtle]

Oh no okay, the overfeeding may have actually been an issue although I didn't think it was because it didn't look like she was pyramiding etc. yeah I did notice that some algae did grow in between her scutes so I always tried to brush it out with a soft toothbrush but to no avail. But thank you so much for your input!