I'm guessing that this is Mg deficiency so I've been spraying it with a water epsom salt solution and it looks like it's doing better but I just want to know what you guys think.I will add, because you have to see in the picture, that there are burns on the tips, the veins seem green while the edges are yellow, the growth on bottom is slow and small, and some of the leaves are oddly formed. Take a look,thank you.
A lack of potassium results in browning leaf tips with gardenias....coffee grounds are a good cheap source of potassium and gardenias thrive with them. You may want to apply the epsom salts to the soil rather than applying to the leaves.
http://www.gardeningknowhow.com/flower/fertilizing-gardenias-in-your-garden.htm
