How often should I water?

The real issue here, is you are half hydro (20% coco + 30% perlite = 50% hydro...) So how to keep your plants happy in this mixture will require some trials and errors. Watering in soil is more of an art than science. Some plants will like dryer soil, and some will do better with more frequent watering. With more frequent watering cycles, the bottom of the containers stays moist and you would water when the first inches are dry. Plants that likes dryer soil would benefit to let soil dry out, and have less frequent, but deeper watering. Usually, plants roots likes to dry as much as to receive water. In a full coco grow, or a full perlite grow (yes you can do a perlite grow) or a coco perlite grow, the medium needs to stay moist all the time to provide the correct EC and keep the right pH. Watering should be done at least once a day, until you gets 20% runoff that should get discarded in a drain to waste setup, or sent back to the reservoir in a drain and flood setup. A best way to start, is to wait until it is dry, do a full deep watering, and watch your plants. A full deep watering would need about 10-15% of the volume of your container in water. Look for signs like wilting. Than a few days later, when the top is dry, but the bottom still contains moisture, try to give half what you gave and see if plants reacts better or worst than with a full deep watering. For growing in organic and maintains the highest level of life in your soil, it would be better to always keep some moisture in the bottom, but this is not a catastrophe if your plants likes it dryer, go dryer. Next run, try to do these test before flowering so you know what your plants likes and what you need to do to make them happy! I went to look at your diary, and yes you need to feed more. Your base soil is depleted and gave it all to bring your plants. 2ml per Litre about 25% of recommended feeding charts, try to give a full dose (30ml a gal or 8ml a Litre) to correct the deficiency, and we'll see where they stands after. Most likely if you don't plan to use the Subterra and Florescence from Motherearth nutes line up, you will have to compensate because they also supply some P and K.