Hi, This is my first grow... I've done a lot of reading on the subject before I jumped in, but I'm having a hard time figuring out what is going on here. My 6 week old plant seems to have leaves turning yellow, then dying from the bottom up. The Ph seems to range from 6 to 6.5 when I test, so I do not think it's that. I'm not overdoing it with nutrients. I water every 4 to 7 days, depending on how quickly the dirt dries out. Is this something that is natural? Something to be concerned about? The first picture shows the plant in general, the second shows the leaves on the bottom turning yellow.