Finding NiMo

20G long, A-0, Nitrite- 0, Nitrate- 10, pH 7.8 9 cardinal tetra, 7 lemon tetra, 4 pygmy cory, 1 GBR White hazy spot developed in flank of one of my lemons. A few males have been jostling and flashing a lot lately, but don't see one or the other being targeted. Not sure if this is injury or infection? Thanks for the help NM

Thanks everyone for the tips

Thanks for the tips, much appreciated. I have 4 live plants, a crypt, 2 red swords and a java fern, I'm nervous to salt and injure them. I've already increased water changes, the nitrate bump is a recent change. What temp range would you suggest? I currently run 79-80 Many thanks for helping a beginner Nick

20 long 7 lemon tetra, 1 GBR, 6 pygmy corys, 5 amano shrimp, 1 nerite snail pH 8.2, nitrite 0, nitrate 20-30, don't remember exact kh/GH, but it's high, 12+ Anyone know what this is on my GBR dorsal fin? It's thick like a mass, not flat. Also a similar small spot on the upper lip. Appreciate your help