Can't be sure about the lower leaves problem, they do start to die in flowering but seems a little early. I'd try flushing it out, you may have a nute lock out and it won't do it any harm even if it dosn't.
I'd guess about 6 weeks till it's done, if your desperate to see what it smokes like you can probably get something decent in about 4 weeks, just choose carefully, don't be gready!
Oh and good luck!