pH 7 runoff is too high. Get it into the 6.5-6.8 range.
Potassium is the 'k' in NPK and is the last number on the bottle. For example a 6-3-4 nute has 4% potassium.
You can foliar feed at any time. You can even use your tiger bloom along with the calmag, but dilute it quite a bit more than the bottle says.