Goldfish Tail

[dredge3]

Hi one of my fish (6 year old) has gradualy aquired a red veiny tail.It has has minor finrot it he past, well mor like a few small spots on yhe edge of its top fin. Its rear fin started going red a year or so ago.I thought this may be my from having a go at it.The from has been there for a few years now so I don't know if thats anything to do with it.
It looks like bloodshot veins going from the ends right upto its body, half a dozen or so.

 

[WILDER]

Septicemia which is hard to cure once it has progressed, need to look at sice of tank in gallons or litrres, full fish stock of how many and which kind, plus water stats in ammonia,nitrite,nitrate,and ph.