Is the ph value of compound carbon source 5.7 normal? Why?

The ph value of the composite carbon source is 5.7, which is normal, because the composite carbon source is an organic matter, which will produce an acidic reaction in water, leading to the decrease of the pH value of water. According to relevant published data, at the same time, the decomposition rate and metabolites of different organic substances contained in the composite carbon source will also affect the pH value of water.