I've developed what I think is a magnesium deficiency in my plants due to pH lockout. I have been trying to get them healthy for the last few weeks. This is my first real grow and until the problem started I wasn't monitoring my soil pH at all. My soil is still around 7.3 despite me feeding with properly ph'd water for a couple of weeks now. The yellowness of the leaves which I attributed to the magnesium deficient seemed like it was clearing up only for it to return in the last couple of days. When I test my runoff I get around 6.5 but placing the probe meter into the soil reads around 7.3 consistently. I'm not sure what else to do as far as bringing the soil pH down. I am using FF ocean forest soil with FF nutrients, cal-mag, and pH down when needed. I pH my feed water to around 6.2 to 6.4. Thanks to anyone who can help.
Two materials commonly used for lowering the soil pH are aluminum sulfate and sulfur. These can be found at a garden supply center. Alumin Sulfate works instantly. Sulfur is slower but a more lasting fix and is what I use in my organic outside grow. BNW
Surface application by hand or rotary spreader would work well and scratch-dig into the top inch or 2 or soil and water in. I just hand sprinkle Sulfur Dust or Prills into the hole as I'm putting the next vegger out to flower. BNW