Leaf tips turning yellow then brown

Fifth week of flower leaf tips turning yellow and brown tips and Crispy down the sides. In soil Foxfarm nutrients feeding twice a week watering daily pH levels checked 6 1/2 to 7 sure it’s a nutrient problem but don’t know which.Leaves are curling and some falling off unwilted handful a day, Skipped feeding for a week just watered problem getting worse.Humidity running 60-64%

temperature steady around 70