help!! branches turning brown/ drying out and dying!!

Need advice now!! I have a 6ft sativa in her 5th week of flowering. She was rootbound and doing quite well for about a week...then leaf tips were burning, entire fan leaves would turn brown and wilt away turning crispy overnight. This girl was doing GREAT during veg using FFOC soil but my supplier was out when i was transplanting for flowering. The soil I used was Scotts hyponex with tracevNPK. When the leaves started burning and drooping I assumed it was nutrient burn and then flushed the plant thoroughly, which only made it worse. I've lost a total of 18 branches due to them drying out and dying. :( I dug the soil out from around the rootball and found that it was extremely moist considering it hadn't been watered since the flushing. I've lost 65-75% of my fan leaves and the upper branches are beginning to show the same symptoms. Does anyone have a SOLID solution to save my baby before she's too far gone??

First time on this forum and haven't figured out how to post the pics...