Pale lesion on clown fish?? Brook??

[kikimango209]

Hi I am fairly new to marine tank as I only have kept freshwaters.
I have one small orange clownfish and this fish developed white~opaque lesion on R) side of its body.
I wasn't sure if it's just body colour change or some kind of infection?
I kept this fish about ~1.5month. Noticed this lesion a few weeks ago. (cannot remember how many weeks).
Does not appear skin peeling, looks more of discolouration.

I did not QT this fish as I didn't have a spare filter for QT tank.
Its tank mates are two hermit crabs, one cleaner shrimp and a threespot blenny.
Should I move it QT tank? Does it look infection or just body color change..? I have a 10G empty tank I can possibly use as a QT (need to buy a filter tho).
So far, it eats well and swims well.

Please give me advice experienced refee-rs!
I lost two clownfish already (no I didn't keep 3 in one tank) and I don't want to lose this one (one jumped out, the other one was bullied to death by this naughty one)

 

[ArtofReefing]

I don't think it's brook, it looks like it could have scraped itself on a rock or something. I'd keep an eye on it just to make sure it doesn't get infected. You can treat the food with kanaplex which cure multiple fish diseases including infections. Just in case.