My brother-in-law (BIL) has had a pet turtle for decades and seems to think he knows exactly what she needs for care. She developed a bright white spot on the apex of her carapace over the past few months that BIL is dismissing as a scratch that will heal; I am no so certain. I will answer these questions to the best of my ability as the turtle is not mine. I believe if I show my BIL this thread, it will convince him to take his RES to the vet or amend his husbandry.
Name and sex: Miss Topsy Turtley (Topsy for short)
How big is your turtle? Shell maybe between 8-9 inches? (20-23cm)
How long have you had it? ~27 years (from hatchling)
What is the water temperature? unknown
Did you use a thermometer? no
Are you using a water heater? no
How much water is in there? unknown
Are you using a water conditioner? unknown
Are you using any filtration? yes
What is the basking temperature? Outdoors temp (turtle kept in koi "pond" outside- more of a koi tank, above ground, no soil/plants)
Is there a basking light? the sun
Is there a basking platform that is easy to climb on? yes, she gets completely dry
What kind is it or what is it made out of? floating, plastic?
Is there a UVB light? the sun
What have you been trying to feed it? turtle sticks, fresh veggies, sometimes fruit or dried worms (from can)
When was the last time your turtle ate? unknown
How big is the tank/pond/enclosure? unknown exactly; I would estimate the size of a bathtub, with 9 inch square floating platform
Is the tank near a window? outside
Is the tank in a room with a lot of activity? not much activity around pond
Is there any other unusual activity/symptoms? She had trouble laying a clutch back in May, so BIL took her to the vet to give her a shot to induce. Still no eggs by the next day, so vet gave her another shot. She laid eggs within a couple hours of second shot. The first bits of white started showing around this time and vet dismissed it at a scratch. Two months later, she exhibited nesting behaviors and stopped eating, but refused to lay. Then she randomly started eating again and stopped nesting behavior, so brother is reluctant to take her in for another expensive x-ray. Now the white spot has developed to the size of an American quarter and it bright white. It is hard, dry, and does not smell. There doesn't appear to be any strong pitting.
Thank you for any help you can provide.