Murky water after a spawn??? Say it ain't so
When Koi spawn they do the bump and grind with each other and anything that is or isn't nailed down.
Needless to say in the process of rubbing against every possible surface they will break all kinds of previously stuck stuff loose and it winds up clouding the water
Add to that all the extra ammonia and protein from eggs and milt
and your water is a smelly, murky, mess
Might as well start a trickling overflow water exchange and keep close tabs on your ammonia and nitrite readings, as a spike is normal.
Do you have a hatchery tub/pond/etc... to move the eggs to? They're gonna do MUCH better if you do.