why is my turtle not eating

by tracey
(uk)

hello i live in the uk and i have 2 turtles 1 a cumberland slider and the other is a map turtle. They have both stopped eating and sleep a lot on their log they have been like this for about a week and half now, we have tried them with different types of food but they are having none of it. We have checked them and they seem fine, their shell is still the same and they do swim around when not asleep. We have the light on for about 12 hrs a day and they are asleep about 8 or 9 hrs of that, my water temp is about 30 degrees c and we do a water change once a week, also we put vitamins in the water nearly every day. They are about 8 to 9 months old, can you please help me as I'm worried about them thanx tracey