How fast is water draining?

Water should not be held in the dirt for to long. It also looks like an over watering issue as well. You get that from trying to correct problems sometime you need to over water. It's a balance act you need to play. Epsom salt can help the mag problem and so will CalMag Plus.

Check to make sure you have good drainage so there is no pooling of water in your dirt. Vermiculite will hold water in FYI. Perlite allows it to drain out fast.