seedlings with tips browning dwc

so I attached some pictures of my white widow and sweet tooth seedlings.
they sprouted on oct 9th, and as you can see there tips are yellowing and browning. what do you think this is? they are about a week old in the pictures,
rez temps are 65
ppm 88
sensi 2 part
ro water
roots havent left the netpots yet
ph is about 5.9-6.2, adjust every day back to 5.6 and it swings back up
thanks for any tips! i can take more pics if necessary

Did you soak your hydroton rocks before you used them? It can help stabilize your ph level.I soak mine for a day or so in water with a ph of 4.When you check the water that the rocks were soaked afterwards, it usually reads about 5.5 -5.8.My ph level in my dwc tubs stay right at 5.8 and never strays more than a tenth or 2.As far as your seedlings,make sure your net pots are submerged an inch or so into the water so your plants dont dry out til the roots start dropping in.What kind of lighting are you using?

no, didnt soak them at all really just dipped in 5.5 ph RO water and shook em out to dry but that was on the 6th, I put them in the buckets on the 15th. once a day I check the ph and its usually between 6.2 and 6.5. drop the ph down to 5.4-5.5 and the next day its back up, its only been 4 days though and the roots arent in the water yet.
the rockwool cubes are sitting where the hydrotron is still wet, but waters even with the bottom of the netpot.

i'm thinking that the tips burning is probably because I would mix the water/ph down right before use. it looks like there recovering, but am I adjusting the ph correctly with my buckets?

also these babies are under a 4x24 watt t5, with 2x45 lpm airpumps and 2x6" stones
600w hps for flower

Ya, soak the hydroton next time. or soak some and transplant it if its still early enough. Its gonna be a pain in the butt till the hydroton stabilizes.

If it isnt nute burn than it has to be from all the PH down you have been adding and the constant flux. They should recover fine. Live n Learn i guess, I did it with my rockwool the 1st time on my clones and wondered why. never do it again tho lol