Plants looking good but ph and ec rising every day?

using a wilma 4 under 600 hps, 4 x15 min feeds, rock wool with clay pepples - both ec and ph rise daily - ec from 1.2 to 1.7 and ph from 5.7 to 6.3. i lower with water and ph down

does anyone know why this is happing?

thanks

That is just the natural tendency, you just need to monitor and stay on top of it.

cheers mate