I have a gardenia with iron deficiency because the soil is probably too alkaline. It has yellowing leaves, sometimes with green veins. I want to increase the soil acidity, so can I add this special fertilizer that is "for acid-loving plants"? The fertilizer has 1% chelated iron and 3% sulfur, and is in the form of slow-release pellets. Will this help? Anything else I can to to correct this problem?