We’ve had a koi pond that we adopted when we moved here 3 years ago. The koi that were here have thrived and been healthy until this last week one died and now today another. They don’t appear to have rot, but they’ve stopped eating. I checked the PH when the first one died and it’s above 8.4 at the end of the day so I’m working on gradually bringing it back down with vinegar, but there is something else going on. I notice bubbles caught in the algae on the surface. The algae has been hard to manage this year. We now have 8 left, I think, in a 3000gal pond with dual waterfall bio filter system. We are novices at this...they’ve just done so well. Please help us save our koi.