Q.I Have A Jasmine Plant That Has Grown Happily For Around A Year But Now Has Browning Leaves And Seems To Be Dying
It’s watered regularly, I have put some plant feed into the soil and even changed the soil in case there was an issue there….

Certified GKH Gardening Expert
If there are no drain holes to allow any extra water to leave the container then this is likely the culprit. Saturated soils, such as the conditions found at the bottom of drainless containers, will lead to infection.
It looks like the disease has progressed pretty far. The plant will likely die. Should you want to continue a rescue attempt, this article will help with their care requirements:
https://www.gardeningknowhow.com/ornamental/flowers/jasmine/growing-jasmine-plants.htm