Brown Edges, Spots, Tips & Leaf Curling

I currently have developed some dead leafs on the bottom of my plants and brown spots and edges on some leaves. For awhile now they have been slightly curling down and/or up on the tips as well and turning brown.

Here is my grow info:
Strain: G-13 (maybe a hybrid)
Moved to flower 2 days ago and changed light from a T12 4 ft. fluorescent, cool white and warm, 4 bulbs about 1 inch from plants
400 watt HPS about 2 feet from the plants
5.5 - 6.5 ph/Piss colored (not exact, using chemicals to test right now, no meter)
18 gal reservoir, Distilled water (adjusted)
Ebb & flow system, 30 min 4x day
GH Flora Series Nutrients, just changed to Transition phase and flushed before hand
8-9 week old clones, four in one tray

I think I have had this problem with every nutrient change. Could it be a nutrient burn and why would this be if I am following schedule? Any help is appreciated...

Thank you!

If that's all you got I really wouldn't worry about it, not all leaves are perfect. Now if it progresses I would maybe start to think something was up but if that's it then your good..

looks to be a slight N overdose. I would cut your nutes in half and see what happens and add more as its needed. you can always add more but ya cant take it back.

agreed.......

Thank you for letting me know it IS a nute burn. So many deficiencies sound like they look the same to me since I am still learning!

Yes, it is only on about 1-3 leafs per plant, but it happens every time I change the nutrients out. It has always helped to flush and to dilute the nutes (which happens anyway as I top off the reservoir which loses about 5 gallons a week).

I will keep doing what I'm doing since they are all over 20" tall now!