I always flush my plants with a solution BUT!! I would like advice on what others do to flush their plants (solution or other-wise). Specifically to not interrupt the fertilizer schedule.
Water and water only oh and did I mention water.
Taps fine just get the PH right let it sit for at least 24hrs to let the chlorine evaporate.
I have used tap water for around 20yrs no problems.
I let it sit in a open container for at least 24hrs and air stone with a small air pump will help evaporate the chlorine to.
i have not flushed yet still on my first grow, but what i have noticed is u want the lowest ppm possible, to help get out all the old nutes with out any new ones, tap water has some nutes, chemicals and other things (bacteria and such depending on where u live) and chlorine, u want the plant to have no trace of the old material. its why u need to use reverse osmosis water over the distilled drinking water as well, reverse OS gets rid of everything even the good stuff, distilled is pretty clean but not all matter is gone, leading to higher ppm. tho not high enough to truly be bad for flushing. and depending on the company they may only distill only once. so u need to check the ppm of the water you are using or get a silent RO to ensure the lowest ppm without having to test, for more on water http://en.wikipedia.org/wiki/Water_purification