new tips turning white/ some brown tips curling up

I would love some input on this. i hope i am not being paranoid!! i am 12 day in flower and plants are doing great overall. however i am noticing the tips of new leaves on the top are a very light whitish color..just the very tips. Some of the middle fan leaves have brown, crispy tips pointing up..once again just the tips..the rest of the leaves and plant is looking good. these symptoms are random and affects a small percentage of foliage but the tips of leaves on most new growth at top of plants are showing white or very light color. Mayby Mag def? some type of nut burn? any input would be great! Here is the growing setup.
4 plants hydroponic DWC and drip in 18 gallon rez in Hydroton. Lots of bubbles. Good circulation. 2 Chernobyl (60/40 sativa) and 2 Kaboom (80/20 sativa)
2nd week of flower running 850 total ppm-
600 ppm Sensi bloom and 250 ppm Flora Nova grow (using for transition for two weeks then going all bloom) and Hygrozym 4 ml per gallon. will increase about 50 ppm per week to get around 1300 or so at end of flower. Gonna start Bud Candy after 2nd week..then Overdrive later.

Closet is 25 inches by 6 feet using 600 watt HPS vented at 14-18 inches from
canopy…lots of fans, good ventilation and air flow. Co2 every 3 hrs for 10 min (fans off for 15)
Temp 77-82 Daytime…68-74 Night time Humidity 35-42%
Average closet temp at 79 while temp at canopy is 80-83
Also, I have not done much trimming since change over except for the following…a few lower branches and leaves at base and a few larger upper fan leaves have been trimmed back for light penetration to lower bud sites..but not much, just a few leaves per plant. Any advice or “tweeking” is greatly appreciated!! Could this just be stress signs of transition or perhaps bigger issues??

Looks like your are running borderline fertburn, to me. Back off just a little, or skip a week before the next increase, and you should be okay.

What is the ppm of your base water? Is it tap or RO? 1300 ppm can be too high for some strains. Have you ran this strain before with the same nutrient regiment? Id add some ph'd RO water (007 ppm) to bring down your overall ppm because you have too much of something. You could also be lacking phosphate and potassium. I switched to CANNA because other higher end products out there were lacking on those. Ive seen this early in flowering too but in my case it was due to heat stress. From what you stated above, it looks like your canopy temps can come down at least 5 degrees... Id start there my friend. Good luck!

thanks guys..Mr matt, my starting ppm for water is only 62. i rarely have to use ph up or down but it does tend to creep up as the days go by. only have to adjust once mid week (i change out every week). Just using 200 ppm of grow and 600 ppm of bloom and a little Hygrozym..so not a fancy brew. brand new strains for me so no past references..the rest of the plant looks robust and healthy. i backed down ppm now to 800 the last few days and keeping the light 18 inches (i put hand over tops and no heat discomfort..barely warm) symptoms are same not getting worse or better..i am hoping it may have been the shock from going 650 ppm at end of veg to 800 plus the nutz switch. thanks for the input i will keep ya updated