Discoloration spot on Dwarf Rasbora

[drossean]

I've had a school of 10 of these guys for a few months now.  I swapped the glass lid for a screen lid for a week during the recent heat wave to prevent temps raising too high.  It of course changed the lighting in the tank.  '

When I switched back to the glass lid yesterday, I noticed a white splotch behind the head of the most active of the bunch, he's never really settled in and always racing around.  Could this be stress related due to changing the lid, or an illness?  Maybe I didn't catch it earlier because the tank was dimmer.  It doesn't look raised, but he moves so fast it's hard to get a decent picture.

Still eating and active, not flicking or acting otherwise abnormal.  There are also cherry shrimp and ramshorns in this tank.

NItrates - 10

Hardness - 100

NItrite - 0

Ammonia - 0

KH - 2

Temp - 74

7-gallon heavily planted.

 

[Colu]

Could be an injury just something to mindful of you can can white patches with columnaris that a gram negative bacterial infection that spreads more quickly at temperatures over 75 and can kill in 24hr to 7 days depending of the stain it's difficult to say off your picture if your dealing with an injury or columnaris if other fish start to show these patches than I would start to treat straight away with kanaplex and jungal fungus clear fizz tabs containing nitrofurazone following this treatment plan @drossean nitrofurazone and kanaplex can be harmful to shrimp so I would quarantine  any fish showing symptoms if you do need to treat