Sick Betta? I'm Not Sure

[Panda_Fluffness]

Please help. My Betta fish called Kaji seems to be ill. He is hiding behind his filter and under his rock. He was fine this morning but now he isn't doing well. He is red colored but he has a discoloration around his mouth. It's white and might be swollen. Any ideas of what is wrong with Kaji???

 

[LyraGuppi]

If you could fill this out, it would help a lot c: 
 
Tank size:
pH:
ammonia:
nitrite:
nitrate:
kH:
gH:
tank temp:
Fish Symptoms (include full description including lesion, color, location, fish behavior):
Volume and Frequency of water changes:
Chemical Additives or Media in your tank:
Tank inhabitants:
Recent additions to your tank (living or decoration):
Exposure to chemicals:
Digital photo (include if possible):