Run-off ph very low

I had the same issue , my input was good but the output was low , It was just after mid flowering so I did flushed her twice but it did not worked so what I did ( and I can't tell if it's something to do or not but it has worked for me ) was preparing 5L of ph'd solution at the good ec range because the previous flush had removed nutz and I flushed the pot inside of a big bucket , I was keeping the runoof which was basicly the 5 previous liters and I was adjusting the ph each time until the input and the runoff ph was the same aka 5.8 ( it took me at least 6 adjustment ). It worked but I will not tell that it's the good method to go with