Koi losing scales and ones fin going funny anyone know the causetreatment Koi

Only noticed this today, checked on them a few days before and they seemed fine and healthy but after going outside looking today I saw this and Im not sure what to dohttp://i.imgur.com/3mTM608h.jpgThanks for any help

I have not, I dont have any of the test kit things to do it but I phoned up a shop near me and he said to put some Medifim stuff into the pond so Ive done that, I guess Ill go out and but some test things and check everything is OK in the water