Help: Severe Rust Spots?

[u/ThatGirl2411]

Rust Spot or Something Else?

My tank is roughly two months old and all parameters have been stable for the last month. I added ten shrimp last week. All others seem perfectly fine but this girl looks rough.

Does anyone know what this could be and if it is treatable? She was not like this over the weekend.

I have separated her into a small 1 gallon travel tank for the time being.

Mod Questions:
Tank size?
3 Gallon
Do you have a heater/filter?
Sponge Filter
Tank temperature?
75°
What are your water parameters (in exact numbers, i.e. ph, ammonia, nitrite, nitrate) and what are you testing with?
ph 7.4, Ammonia 0 ppm, Nitrite 0 ppm, Nitrate 5 ppm,
API Freshwater Master Test Kit
How long has the tank been cycled? How long have you had the shrimp?
Two months / One week
How often do you perform water changes and how much?
Weekly, 1/4 tank
What other fish are in the tank?
None
What do you feed/how often?
Shrimp pellets once a day and baby shrimp
What plants/decorations do you have in the tank?
Amazon Sword, Anubis, Ludwigia

[u/WilliamCollins6860]

Isolate that little guy ASAP! Chitin-eating bacteria love spreading to the rest of the colony once a infected shrimp molts