Hey Jenny, Buds that do not open could be a symptom of many problems - so its best to take a cutting to your local nursery to discuss the conditions you are growing in. Some gardeners say that adding a 'Bloom Booster' fertiliser that has increased levels of phosphorous in it can help, but we disagree as the extra chemicals generally just go to waste or put your soil into imbalance. A 'tonic' like Seasol or other seaweed based products will always be best as they are rather benign, but boost bug and microbe populations in the soil which then in turn help release the natural elements for plants to take up.