Injured Fish - Need Help

So I woke up yesterday morning to the below picture. To me it looks like she has ripped her top lip. There are 3 gouramis and 4 Molly's in a 30 gallon planted and gravel tank. Intake tube has a prefilter so can't be that. No fish are aggressive. One Molly chases the other mollys during feeding but she doesn't bother the gouramis. The injured gouramis is still eating. Has anyone seen something like this? Ammonia 0ppm, Nitrites 0ppm, Nitrates 5ppm, pH 6.9.

 

Not sure what caused it but I have had fish with similar unexplained wounds. I dosed with Seachem Stress Guard. It is an antiseptic.

 

I will pick some up and try it. Appreciate the information.

 

I’ve never used Stress Guard. I’d keep the water clean as possible with frequent water changes.

 

Will do thanks for the suggestion.