I thought ph in soil was supposed to be higher--7 being ideal. Also I found with my grow that after awhile the soil just ran out of nutrients and I had to feed more of them after about 6-7 weeks. I did seem to have the same problem in my hydro grow (low ph) because I was spraying them daily with seltzer water with a very low ph (3.8). They did get nute lockout, turn yellow, edges curled etc like yours but even after I fixed the problem the affected leaves didn't return to normal. However, the new growth looked fine. AND (as if I haven't talked enough) I believe you want a higher phos. content for blooming.