My gardenia has buds but they die before they open, why?

https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-flower

This is a common problem of gardenias, so don't feel bad. A professional who gives advise on the radio says put a tsp of hydrogen peroxide + a tsp of vinegar + plant food into a gallon bottle of water. Water your gardenias with this mixture. They are really very fussy plants and you can't let them get too dry. See how this works for you.

I also put mine outside for the summer under a tree for some shade they like to be fed with an acidic fertilizer for Rhodenudriums, azaleas and other acid loving plants keep them watered several times a week especially during hot warm weather

Thank you very much!