The claw is from low ph, the burn is from overfertilizing.

When using the Fox Farms line, keep in mind that the necessary micronutrients are in the Grow Big and the Tiger Bloom. Big Bloom is nothing more than a catalyst tea designed and formulated to compliment the other two, but is lacking in the micronutrient department.

Check online for Fox Farms Weekly Feeding Schedule. A "water, water, feed" schedule can easily lead to "water, water, overfeed". Pick a feeding day and stick to it. Plain, properly ph'd water inbetween if necessary. Quite a few nutrient products are labeled as if it is a stand-alone nutrient, and Fox Farms is one of 'em. Always check online for the company's feeding schedules, regardless of the company or product.

CalMag is nothing more than synthetic unsulphered molasses.
Use care when using the other additives you mentioned. If overdone, they can kill.

I haven't heard of the FFOF being too hot for flowering. Just keep in mind the slow release of the nutrients when you resume feeding with flowering nutes. (half doses to begin with...) Yes, you do want to restrict nitrogen in flower, but there isn't enough in the soil to worry about.