Could be wrong but looks more of a nutrient lock out possible zinc/ heat... the only way to tell it to look under the bottom of the leaves they like to hang out under there. i would feed just water and (N) for an feeding than add silica to your mix.
hope this helps
St. Isidore Kouzen Zaka
Reality is what you believe it to be.
It's what you put your thought and energy into,
because your hands physically manifest thought.
So your world becomes what you feel and what you think.