A 200 litre tank appears rather small for the size of turtle, even more so if you have a YBS in there as well.
Did you test the water quality with a test kit? or go on appearance? Water can be crystal clear and deadly toxic at the same time. Given the feeling that Mississippi Maps are sensitive to water quality, I make sure I monitor with a test kit on a weekly basis to ensure nothing is amiss.
Using water conditioner with water changes will help prevent irritation.


