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How big is your turtle? around 17 cm
How long have you had it? 11 years

What is the water temperature? 66 F
Did you use a thermometer? No
Are you using a water heater? No, I usually take my turtles for sunbathing every morning (7-9 a.m.)
How much water is in there? around 50 galons
Are you using a water conditioner? Is anti chlorine is water conditioner? If not, then no. I'm just using it through (for last 2 days).
Are you using any filtration? No

What is the basking temperature? 84
Is there a basking light? Yes
Is there a basking platform that is easy to climb on? yes
What kind is it or what is it made out of? wood
Is there a UVB light? No

What have you been trying to feed it? shrimp at the moment, since she only want to eat that (but started to not eating it through). I still try to feed her pellets or veggies (she doesn't want to eat them)
When was the last time your turtle ate? 5 days ago.

How big is the tank/pond/enclosure? I'll post about this later. I never measure it, since it is large enough
Is the tank near a window? No
Is the tank in a room with a lot of activity? No

Have you read the Basic Care section? Yup
Have you searched the forums for similar situations? Yes, but I don't think I get any answers
Is there any other unusual activity/symptoms? In first post

Are the eyes swollen too? Does she open her eyes when sunbathing?

Sorry for the late reply.

First, my turtle is cured now. And yes, her eyes were swollen. She was still opened her eyes, but few days after I post this thread Her eyes swelled so bad she couldn't open her eyes anymore.

Fortunately after some research, I found some bloggers recommended Betel Leaves (it's quite common plant in my area, South East Asian and South Asia). It is really worked like magic! If you had any chance to try this, don't feed it to your turtles. Boil about 4-5 leaves and soak the sick turtles to the water (from boiling the leaves, don't forget to cool it down), along with the leaves too. Soak them overnight. The effect may not be seen in 1-2 days through.

Problem solved now. Thanks Steve for the reply!