Question
I have 2 Jasmine plants which a few weeks ago suddenly dropped the majority of their leaves. One has a single flower starting to emerge now. They receive light all day, as they are in the southern exposure of our house. We thought at first they were root bound, so we repotted them to larger pots, but they still are doing nothing. We keep the soil moist and give them organic fertilizer once a month. The stems still are springy and there are new buds set up as if they wish to recover.
Thank you for your time on this matter.

Answer
Ed,

You didn't say what variety of jasmine you have and there are several. Leaf symptoms such as yellowing, browning or dropping are the most common signs of trouble, but the same symptoms can be caused by different problems.

Stick a fingertip into the compost to check moisture levels or use the probe of a moisture meter available to determine if watering is the problem. Then either soak or drain the plant accordingly. The plant can seem dry on the surface but have a lot of moisture lower in the pot. You also didn't say how long you have had these plants. Be very careful about the watering. When you repotted them how were the roots?  Were they wiry looking and were they rootbound? Or, were they not as bad as you thought? How much larger a pot did you move them too?  Going to a lot larger pot makes it very easy to overwater.

Lack of light as the sun gets higher in the sky may be to blame if growth is pale and spindly, flowering plants do not flower or the foliage on variegated plants reverts to plain green. You didn't say where you live. Moving the plant outdoors for the summer is the answer if it is a light problem. Most blooming plants love the sun and love to be outdoors for the summer. Just bring them back in if the lows dip below 50 degrees.

Leaf dropping can also be caused by a fungal problem.  Just in case I suggest you spray them daily for a week with Lysol spray, name brand or generic. Thn spray every other day until you see signs of growth and new leaves. Make sure when you spray them that you get the fronts and backs of all leaves.  
Good luck,
Darlene