It looks to me like you have some sort of deficiency aswell as maybe a small bug problem, i could be wrong but certainly looks that way, also you can use nutes from day 1 you dont really have to wait that 2 weeks of using normal ph'd water but test your water run off ph this will give you a better idea, the issues arrise from nutrient lockout being a ph problem, you state you use a ph of 6.5 i always go lower than that usually around 5.8 as is guided by 'canna' and my nutrients have never locked out once and that is from feeding from day 1, i can only give information from my own grow and what i know to be true for me but my suggestion is give them a flush for maybe 2 days and use nutes as normal after this time with a water ph of between 5.6 and 6.0 and see what happens you should see a big difference
Steve