How often to feed coco 60 40 clay pebbles

You should feed in coco everytime, unless you are using some crazy stuff :p Coco has no nutrients. If ill-prepared coco, it'll leach Ca++ and Mg++ from your fertilizer for a long time and cause thos deficiences, which take ~60 days to present themselves visibily... Also, can cause a K-toxicity when it is supplanted by the Mg/Ca ions with stronger affinity to the CES. So you end up with sickly PoS for 30-40 days. LoL. Anyway, you need to provide nutes every time. Early on, you could re-hydrate, but fertilizing and allowing enough run-off will avoid toxicities. If you are in a too big of pot for the plant size, you don't want to be fertilizing the areas where no roots exist for days or weeks befoer they get there. So, some common sense is required here. There are contexts when you want to feed with simply pH'd water. If i see some darkness creeping up on plant, i'll give a dose or 2 of ph-only, otherwise it is nutes everytime. I don't go crazy with ppms. Simple jack's as instructed. In fact, been using 10-20% less for a couple grows and i no longer see any darkness creeping up on plant - it was rare to start.