Hi! I too fed heavily in Coco. EC around 1,8-2,2 but it never worked out for me as good as I would like to in last two years. But my most recent grow I was told to lower the feeding to about EC 1,4-1,5 and it worked like a magic. Plants grew absolutly amazing with now problems and deficiencies 
I fed them every watering and with almost no runoff. When the water started to Come out from the pot a stopped.
2 galons of water for my 10 galon pots was standart in flower.
I started to feed the seeds with EC 0,6 first week. EC 1,2 second and third week and EC 1,8 max at week Four and full grow until I switched to the flower cycle. Then I checked the runoff everytime until the build up started and then I lower the EC from 1,8 to 1,4-1,5 until the end. My grow cycle usually takes 5-6 weeks. No runoff, no flush. Only two flushes last week. This worked out really great for the plants I used advanced nutrients pH 5,8 and Mammoth microbes.
Check out the grow
Good luck with your next grow keep growing