Coco/perlite run off

A good flush a 5 gallons or so of water ph to the the zone you want

I would flush with plain water and then wait 3-5 days for the soil to dry out a bit. After the drying period I would feed as normal 💯

Set up a fresh well balanced nutrient solution with the right ec and Ph and flush it with this instead of calmag only till input equals runoff and your good. Measuring runoff ph is btw also a good idea. Make sure to have always enough run off when feeding, always feed with your full solution with cal mag (base nutrients and calmag is usually enough) coco/perlite should be treated like all soilless growing media, you need to work with your drybacks in veg irrigate frequently in generative stage give longer drybacks with higher EC on the roots. Imagine when you feed your plants take up water + evaporation leaving salts in your rootzone and btw plants also release ions themselves while absorbing nutrients what you can see in circulating Hydrosystems. An EC of 2.1 is not super high for plants older than 4 weeks if everything else is fine, but if its to high for your setup reduce your dryback to keep input EC/PH closer to runoff EC/PH. Every time when you have the feeling something is out of whack having lockouts and stuff you can do this longer irrigation till Input=runoff to renew what’s inside your pot. But be aware that these are events were you overwater but since you went semi hydro with coco/perlite its not that harmfull. I use to pump air in my nutrient solution and at times also used hydrogen peroxide to have more oxygen supplied to the roots on these occasions.

not a big deal just low down your feed by 25% for 1 or 2 feed and you should get back on track