re: Gardenias turning yellow and losing leaves

Currently fighting the same issue with mine. They are older bushes and I transplanted them in April of last year. Transplant shock + heat rocked them pretty hard. I got my soil tested a few months ago and the nutrient content was great, but the pH was 7.5. I amended with sulfur to get them ready for spring. A couple seem to be doing a little better now, but hard to tell just yet. I just sent another soil test in to see what effect the sulfur had on the pH. I’d recommend starting with a soil test, because all of my research has led me to believe that gardenias are more picky than most any other shrub when it comes to pH. I just like the smell a lot so I’m trying to figure them out. Hopefully this year they do better.