Urgent Care :: Possible Shell Rot and or Fungus

[Amsterdam]

I have neglected my turtles, due to my current school schedule, i have feed them though. During this time i think one of them has developed shell rot or fungus. Their water is not clean due to the filter clogging. I know i messed up but i have since cleared my schedule and want to know what is wrong with my turtle. He is 7 years old and has not had a problem like this from what i recall. I will try to post pictures as soon as i learn how to, as i am new to here.

He has large whiteish spots on the shell, it appears as if it is really dry.

i have no idea what it is or how to treat it please help

[steve]

It mostly looks like fungus, are there any soft or smelly areas?

[Amsterdam]

It has a musk like smell to it

[steve]

The fungus hasn't spread much at the point but it moves quickly. I would address all the problems with his filter/tank then treat the fungus.

[Amsterdam]

Thank you for your help
i started treatment today
i'll post some progress photos in a few days, when things start to change

i've also cleaned their entire tank and fixed the filter