If yellowing is caused by bad pH, it can stop them from living. Or at least reduce yield. Not saying thats what yours is caused by but I'd keep an eye on it. I just put a post in the plant problems area seeking help with my pH problem. Maybe when the experts chime in I'll learn something

If you don't already have a pH meter or test strips, get em now. In my opinion it is absolutely necessary to know the soil pH. It gets more important as the plants get bigger too.