Problem with Pixtures, Please HELP!

Necrosis showed up a couple of days ago on bigger fan leaves. My first thought was Mg deficiency, but ive been feeding with Botannicare Pure Blend line, as well as Cal-Mag from Botanicare. Feeding almost full strength every other watering. pH of my water/nutrients is balanced, but run off is extremely low, around 5. I flushed my soil yesterday with many gallons of water and couldnt get the pH to get any higher. after pouring about 8 gallons through a 3 gallon pot I called it quits.

If any one has any suggestions, help, or concerns, please feel free to let me know! +Rep!

add some lime for ph adjustment.

But do you think thats the cause of the necrosis?

BUMP! anyone?

C'mon!...anyone?!