My 2 koi are dead

ok I am kinda a newbie here i did have another account her somewhere anyway
I have had my pond about 5 years ill post photos in a sec.4 koi I feed them and they are all healthy well I go out and find my 2 biggest @2ft and oldest 3yrs old koi dead.the other 2 are fine and the 2 dead were too less that 24 hrs ago.
I have a large lily some algae a bio filter and a UV filter. no problems in 4 yrs. no gill or fin problems and no visible sighs of injury, so im stumped who thought you could get attached to a darn fish? raised those 2 from minnows and even revived 1 that jumped out of a holding tank a few years back.

So sorry. I bond with mine, too. It's really wrenching to lose any. Wonder what happened.

Um....it looks sounds like your pond is pretty healthy and the koi couldn't have died from injuries or diseases. Although, do you check your pond for the pH levels and nitrate levels? Most new koi owners don't know that high levels of pH and nitrate levels slower kill your koi over a period of time ranging from days to years. Hope this helps!

I ll check them last time i did all was good just strange that 2 died at the same time ad 2 are alive and well

Sorry to hear about your Koi, it is hard to know what happened long distance, especially since you had them for a while. hope you can solve the mystery, ph, sudden pollutants, could contribute, but it's a guess.