Q.Experiencing constant problem with Gardenia
Last 2 years I have been struggling to grow gardenia plant. One plant died with leaves turning yellow. I bought another one. Based on recommendations, I kept soil acidic using Iron chelates. I also put some Epsom salt to fill magnesium gaps. Plant grows lots of buds and then falls. I sprayed insect soap but not working. Attached is the picture that shows current problem. Any suggestions are appreciated. You send your suggestion to my email smattu@hotmail.com

Having the correct sunlight and humidity indoors for you Gardenia can be a challenge.
It looks like an infestation of scale and aphids on your plant. I would wash away as much of the issue as you can by rinsing the leaves.
Then treat with Neem Oil. You will need to make multiple applications.
Here are some links for you.
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/growing-gardenias-indoors.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/control-plant-scale.htm