cannabis in soil LOVES wet/dry cycles.....the sand is preventing or slowing the movement of air [oxygen ] through the soil and may be the cause of your problems. did the mag u read tell u that some kinds of sand r TOXIC to ur babies?did it offer alternatives such as perlite or DE ?my tip is get rid of the sand and let the soil dry between waterings,,,,,use ph'd water and if bugs show up kill per advice for that specific bug.