Black raised spots on feeder fish

[Lemassa]

Hi! My 11 year old feeder goldfish is developing large raised black/red splotches on his side that I believe are blood-filled and I cannot narrow down what it is. He developed the same thing around this time last year and it wasn't helped by water changes every 3 days, addition aquarium salt added or by ick treatments. it kept getting worse and I eventually treated it with minnfinn and it disappeared in a few days, I know this treatment can be hard on fish so I would like to discover what the issue is so I can find a safer treatment. I believed last year it was something brought in from a snail bought from petco (bad choice in hindsight) but there have been no new additions and that snail has been gone for about 10 months. 

the tank is 25 gallons and has two feeder gold fish, both 11 years old 

all water parameters are normal

temperature is probably between 70 and 78 (I don't have a thermometer) 

a 25% water change is done every two weeks

I understand my tank size is not exactly suitable for 2 large feeders but I have no other options at the moment

his behavior never seems to change, still vey food driven, and active

[Colu]

What exactly are your water parameters and can you take a picture of the sick fish.it will help with a diagnosis

[Lemassa]

@Colu sorry I thought the picture was in the post but apparently not, so here it is again. 

upon a retest done this morning 

PH: 8.2 (a bit high but unsure if its causing the problem)

ammonia: 0ppm

Nitrite: 0pmm

Nitrate: 40ppm

[Colu]

That looks like a possible injury the black marks are a sign it's starting to heal

[Lemassa]

@Coluthere was not a visible injury, it started as a small flat black mark and continued to get larger and eventually became raised after a few days

[Colu]

It could be some form of internal bacterial infection you could do a course of kanaplex in food