Plant Problems.. Heeelp

I noticed today that some leafs on 1 of my plants turned brown and shriveled up... I looked at some of the budding sites and they seem to have turned somewhat brown too... And I noticed one other leaf on another plant that had done the same thing.


Is that nute burn or what? I was feeding them All Purpose Miracle Gro for the veg state now Im using Plant Prod 10-20-10

Then I noticed some white powdery shit on one of the tops on a different plant... I think its mold or powder mildew. If I cut it out should I be ok or am I fucked :/ I didnt see any other spots on any other plants and the weather is nice hot and dry today and there is a nice breeze where my plants are. Is there anything I can spray the plants with to prevent mold? I reaaally dont want my crop to turn out shit filled with mold.

Looks like heat stress/ nute burn. Since its affecting the upper new growth I would go with an immobile element like Calcium. U givin em any Cal-mag or epsom salts? Most companies (I can't understand why) that market fertilizers and soil for weed always seem to lack calcium-magnesium which they all know weed plants love. Why they do this I will never understand.