Hey I am new to growing and have just set up my system, its a recirculating system with just one seedling in it. The problem is my Ph is fluctuating alot, I put it down to 5 but then within a few hours its back up around 6.5 and rising. Is this normal, I know recirculating system do fluctuate but this much?. Im using a bluelab Ph/Ec meter, and rain water. Hope someone can help. Thanks