I was using 100% Happy Frog Soil and watering on the low end of the scale with the BioCanna line and burned the shit out of my plants. I would say if you are using over a half and half ratio of soil to soiless or amendments like perlite, Then give the plants a little while to take out the nutrients by just giving them water.
After the last few months of tinkering with it, I use a 1:1 ratio of Happy Frog to Pro-Mix. Basically in a 10 gallon bucket, I am doing 5 gallons of Happy Frog and 5 gallons of Pro-Mix Orange. My plants accept the nutrients while feeding very well, they grow vigorously, and haven't burned. I have been upping the dosage on my feedings also and am starting to get into the heavier side and the plants love every minute of it. I am very happy with this current set up.
I also use the whole Fox Farms line including the powders on another set of plants. I would recommend at least using the Big Bloom and Grow big like it suggests, and then use Big Bloom and Tiger Bloom in the flower. We have had great results with it. If you are using Pro-Mix then the plants take the nutrients perfectly and remain happy all the way through the cycle. I must say that the Fox Farms line is very straight forward and easy to use. If you are using a Soil like OF with the nutes, then you will have to tinker some.