why do my florescent bulbs blink on and off slightly but constantly with the switch off.?

Likely from the L.E.D.s. I have noticed mine do the same on a circuit with switches with NEON back-lighting in them that switches dual socket lamp fixtures. Strangely enough, however, removing one of the bulbs resolves this unfortunate issue. These are C.F.L. bulbs that I am referring to and hopefully you are as well, and hopefully this information may help to resolve your problem as well.

Through the LED on the light switches.

To light the led the current needs a path to neutral, and it finds this through the load, which is your light fixture. If you were using incandescent lighting the current would be too low to heat the element, but the current through the ballast is high enough to charge the capacitors in the ballast, then discharge through the lamp.

The same thing happens with some occupancy sensors.

In the states the 2011 Electrical Code requires the neutral be present at new light switch installations to allow the installation of sensors that won't produce this nuisance flicker.