It's true that the underlying cause is always in the tank and an infection is caused by weakness/stress
Although I will say that this is not one they just get over. While not life-threatening, the lumps will come and go, causing the fish to always be slightly weakened
Any new fish will also be affected
I have been dealing with this since January and used Lifeguard and an anti biotic before finally figuring out that it's fungal
There was even a period where the lfs
said it was viral and I should do nothing, so now my new harlequins have it too.
I would treat and save the headache