Help, messed up leaves!!

Hello everyone, i'm a newbie and need some help!! Problem; yellow burnt leaves on edges and spreading in. I'm gonna post pics of the leaves so you know what i'm talkin about. I read a lot of posts and troubleshooting pages but i keep getting more confused! First of all I did mess up my nutes the first 2 res changes, then flushed for 4 days. This is end of week 6, swithced to 12/12 Sunday. My room temp averages 73-76, humidity about 40. Feeding Gen Hyd. 2-2-2 (transition to bloom, according to bottle) twice daily (6am, 7pm) ph 6, distilled water. Air cooled light, exhaust out the roof, oscilating fan. WTF is up with these leaves... Mag, Nute burn, overwater, not enough water.... Totally confused!!! Also, should I feed during dark hours?
Any advice greatly appreciated. Thanks!
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Sounds like nut burn. Prune yellow tips to conserve plant energy for buds. Be advised though, leaves will naturally yellow nearing the end of flower phase. Also, do yourself a favor and run pure distilled water for last two weeks before harvest. Flusses that chem taste out of your finished product.

pics would help.

I have a blueberry mother plant and a arjons ultra haze.The problem is that the blueberry seems to hahave yellowing at tip of each leave this is only happening on the blue berry not the other mother none of my clones that are about 20cm tall have nute burns i have always fed my soil plant same has my hydrophonic plants.i was a little clumsy last few watering and got feed on leaves could this be it has i got more on blueberry.cheers