I'm pretty sure the prob. is the MG or pH. I believe MG lacks micro-nutes. Get some Peters All Purpose. That is what I used when I grew in soil. Don't forget to flush that MG out before you start using the Peters. Also get a cheap pH tester and read up on the importance of pH. Actually I would check the pH first, because without it being correct nutes are no good anyway.But I would still 86 the MG.
Also pH is VERY important in hydro. I would bet that is where you failed with it.
You would be suprised at the amount of useful info there is on this fourm if you took the time to search, read and ask before starting to grow.
I wish you luck on this and your future grows.
Peace Out :hippy: