Hi, the pH value should be between 5.5 and 6.5 in coconut substrate, with 5.5 being the target during the growth phase and gradually moving towards 6.5 as the plant ages and transitions into flowering. However, if it’s a bit below 5.5 at the beginning, it’s not that bad, just make sure it doesn’t drop below 5.2. I used to grow in coconut substrate for a while, but it’s not really my thing. I prefer regular soil. What’s important with coconut is that you always give it nutrients since it’s very likely sterile. Good luck!