plant prob

has anyone ever used tap water and had a mg problem

no but a ph problem

Your tap water might upset the pH balance. Let tap water stay at room temperature 24h before watering in order for the chlorine to evaporate. If your pH is off course, your plant can lock out some nutes and minerals.

If this is not your case, buy some molasses, it's a cheap, organic and effective source of minerals, especially Mg, Ca, Zn and will surely be beneficial for your plant. Just add 1 full tablespoon to 1 gallon (3.7l) of your typical watering mix.

Then on the other hand....some city water suplies use an additive called chloramine which bonds to the chlorine molicules to keep them from evaporating......the only way to get rid of chloromine is to boil the water for at least 20 min.. Or filter thru activated carbon.......hope this helps