Hello. So I've been overseas for the past year and my father has taken care of my turtles while I've been gone. I'm home for a short vacation. I've notice some discolouration on one of my turtle's shell. As far as I know he hasn't been doing anything different, other than forgetting to add the water conditioner. The other turtle doesn't have any problems on their shell (they're in 2 separate tanks) and both have some algae in their tanks.
The turtle seems to be acting and eating normal. We don't live by a vet that specializes in turtles. So if anyone can recommend any products or medicine I can use, I'll buy them ASAP and tell my dad what to do before I leave.
https://imgur.com/gallery/SB84H
Thanks for your help.