how are you taking pH of the soil with a liquids only meter? ... that said, you're not using any nutes, in a soilless mix? that has little to no nutrient value,..one reason why the buds didn't form up well,... as for pH, many things influence soil pH once in the pot,.. roots, microbe activity, etc,.... water is onlt part iof the equation, and at that pH, it's sounding like it's soft water, low mineral content, meaning low CaCO3 which is involved in pH buffering,...