Actually he's kinda right. I ONLY use MG time released soil, I love the stuff you just have to know how to use it. The reason you got nute burn is because you over watered you plants. Also if you you want to use MG time released soil, you have to veg for 2 months, and ONLY WATER when DRY!!!!!! Can't stress that enough with this soil. It's as he said, if you flush, you're just gonna make things worse. If you read the bag it says will feed plants for 3 months, but I don't give my girls a lick of nutes for 2 months, MJ is a very voratious plant and loves nutes, so my soil is ready to start feeding nutes in 2 months. So just feed with water till she gets better.
To flush you use 3 gallons of water for every 1 gallon of soil. You can try to flush but I wouldn't recomend it. I'll show you the plant I'm growing right now in MG.
Not a bit of nute burn eh?