Neon Tetras and Dwarf Gourami

[Acohen]

Hello everyone, I have ordered the med trio but I am unsure on how to actually diagnose and treat my tank. 
20 gallons 

1-powder blue dwarf gourami

1-clown pleco

9-neon tetras

ph-7.2

ammonia- 0

nitrites-0

nitrates-20

My dwarf gourami looks like he has scratched himself on one of the rocks. He is missing some scales and his fins are little messed up. 
The tetras are looking not so good but they all eat and swim like they always have. 

I guess my question is, how to I identify if this is a fungal or bacterial infection? 
 

[Colu]

Could bacterial component spots look raised could Also be deal epistylis that feeds off of gram negative bacteria on the slime coat of your fish and spreads more quickly at higher temperatures  what I would do is a course of maracyn in food feeding a small amount twice a day for 7 days as you have it on way  and  dose the tank with ick X I would Also get holed of maracyn2 just in case you need to follow up @Acohen

Edited April 23 by Colu