Anyone who thinks senescence is not a "Natural Occurrence" needs to listen to "Dust in the Wind" by Kansas
Senescence is inevitable. Cannabis is an annual plant in its native climate(s). When senescence takes place in a plant can vary from strain to strain and from plant to plant and is directly affected by its environment.
Will your plants start dropping their leaves in another 14 days of feeding it just water? Depends on the average flowering time of the plant. But, The plant will most certainly suffer from senescence before it reaches the end of its life.