No this is not normal and it is a sign of the turtle having a problem. Thing is it could be a couple of things including a nutritional issue or an infection.
As they are being very fussy about food you need to figure out how to load the food they will take with the vitamins and minerals they need.
You can try treating the eye with diluted boric acid eyewash or sulfamethiazine. The water in the tank needs to be kept clean to avoid new infections.
You can read here on the feeding and care of these turtles
http://www.geocities.com/margareth100.geo/res.html#Health%20and%20disease
and more here on eye problems
http://www.fishpondinfo.com/turhealth.htm#eyes
If you are uncomfortable medicating them at home you may want to see a herp familiar vet and this site may help you find one
www.herpvetconnection.com
Hope this helps you!
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