Question about foliar feeding to correct deficiencies

My soil pH was too low causing a sulfur deficiency. They are about 6 weeks old. They are in soil. I flushed them yesterday and balanced out their pH soil level to a 6.8. I have a sulfur deficiency going on and I'm treating them with a foliar application of epson salts at one tablespoon per gallon ph 6.5) which was recommended from my grow book and guides. But it doesn't tell me how often. How often do I spray them? Everyday? Every few days? Twice a week? Once a week? I don't want to over foliar feed them with the epsom.