What is this white scratch on my platy?

[Sopvmia]

Hi,
I currently have two platys in my quarantine tank. At first I thought one of the platys had ich because it was a fuzzy white dot, but then it turned into a white vertical scratch. Just started general cure just in case. Unsure what it is. Please help.
pH: 7
Ammonia: 0
Nitrite: 0
Nitrate: 20
5 gallon tank

 

[TheNacho]

Hi, is the platy acting as normal? Any lethargy, loss of appetite? Anything with the other platy?

 

[Sopvmia]

Hi, is the platy acting as normal? Any lethargy, loss of appetite? Anything with the other platy?

Hello,
The platy doesn’t seem to be acting strange, it darts away when I get close to the tank. The other platy without the scratch hides behind the filter. Today I noticed the platy without the scratch was hanging at the top of the tank, as well. Both are eating normally.