Answer: I think your struggles point out the fact that gardenias are not that well-suited to our climate. They like moist acidic soil, which we don't have. They are sensitive to salts, which we have alot of both in our soil and water. The browining buds may be a sign of salt build-up in the soil. (Fertilizers are also high in salts.) Leach them once a month to push salts past the root zone. Gardenias are a "fussy" plant, and you are doing what is recommended, so to keep them growing you will have to keep up that maintenance.
Q&A Library Searching Tips