help! well cared for/loved mandarin in trouble.

[icyuod2]

i have a mandarin in trouble. im not going to get into tank size etc, cause i need help, not attitude
i keep 2 mandarin in a small system and i have for 19 and 18 months. both eat frozen foods, (mysis,cyclopeeze,ocean plankton)
but have a ready supply of live cope/iso/amphipods as well as live mysis,rotifers and baby brine 24-7
100+ lbs of lr for a feeding ground.

i noticed today my mandarin (small female-18months in tank) has a large lump on her face. i cant see a visible wound. no hole from a parasite, just a large lump (i think this happened quickly-last 2-3 days)
i've attached pic's

it hasn't slowed her down, i dont think its causing too much pain, she's very active and still eating. upon occation she'll bump it against the glass/lr and she doesn't seem to dart/jump. no scratching or flashing. seems her happy go lucky self. i havent added anything new tot he tank in months. the other fish are problem free. (fire fish, perc's)
help!
now i have a mandarin with a hole in its head (was that way when i purchase him 19months back-never healed, never slowed him down)

and a mandarin with a lump.

 

[icyuod2]

today the growth has a small white dot, dead center of the lump.

 

[Sk8r]

Two possibilities I can think of. 1, a localized bacterial infection that may cure itself. 2. a parasite. Unfortunately, treatment for those two things isn't the same. I'd say watch her habits closely while trying to get a better answer.