Here in the UK we wait until the temprature reaches 10c-15c before we feed and only then small handfuls of food to start with.
At this time of the year you must feed to start off with Wheatgerm until temperatures have warmed up good and propper only the can you start on the summer foods and feeding patterns that we each have.
Try adding in some chopped or liquidized Garlic to the wheatgerm pellets , for one koi will go at this like cats to cat nip....
It also helps if you have any koi off their foods but more importantly makes the koi unpalletable to the Parasites , you can if you look out for it get wheatgerm and Garlic ready mixed NTLabs does a very nice one which we we use .
Later as I previously said you can the start the summer feeding
rgrds
Dave