> What is EC ?
> My plants are 1 month old , Ive never let runoff water, and im starting to see some nutrients problems (like curling tips) so it might be because of not allowing runoff water ?
The link Rosetta Stoned posted is a good intro to the science of nutrient measurments. Here's one here at GWE:
http://www.growweedeasy.com/ppm
If you want to get really good results, you should probably buy a PPM meter, a pH meter, and a bottle of pH calibration fluid, and learn how to use them. You can get cheap ones at Amazon for about $60 total, and with some instrumentation you won't be flying blind but know how much you're putting in and how much is running off.
But to answer your question, yes, you should probably always water to runoff. That way you know you wetted all your media (soil, coco, whatever) and that some is washing through (which you can test and monitor. Keep a notebook!).
If you're getting curling tips you're simply overfertilizing. Stop now and flush some water through the pots to help rinse away the excess.
Have read through all of the growing information here at the GWE website? This is the best cannabis growing site on the web, so read up! Here's a good place to start:
http://www.growweedeasy.com/cannabis...tarted-growing
Happy growing!
PS Photos of your plants always help when you post a question.