yeah man i think also lack of N due to what ever reasons, i sufferd this fate on me last grow, she managed to get to the end but she was a indica strain and did not need as long as urs will,, this time i fed them in veg and there first 2 weeks of flower i continued with veg food so i had enough N to see her through, they do get worse as the weeks progress if u cant fix it, but saying that i got 4 ounces of top dry bud from my girl who was in a lot worse condition to urs !! so soilder on try get some more N in there so she as enough for the journey,, by the way i dont have a ppm meter either but they are a crucial bit of kit for those who have them as they can tell u how much food ( disolved )is in ur water, to much = nute burn to little means food defeicent, so noing the parts per million is rarther inportant when trying to diagnose any problems, i will buy one myself when i av the pennies!! anyhow back to ur yellow leaves maybe up ur ph to the more popular number of 6.5 see if this helps with uptake of ur badly needed NITROGEN !!! good look man hope it works out for ya and in my own personal experience it will m8. grow on, peace !!!!!!!!