Black leaf tips and chlorosis of new growth. . .with taco-ing leaves

Just moved my juvies from under a fluorescent in small soil pots into my bucket hydro constant drip system under a 600W MH. Lights are on for 18 off for 6. I have a 6" fan pulling air through the enclosed reflector 24/7 to eliminate humidity effects and maintain temperature. The strain is Mango Haze and they're about six weeks past emergence.

I prepped the hydro buckets and filled the reservoir with filtered tap water and Fox Farm nutrients and a Cal-Mag addition then adjusted my pH using general hydroponics pH down granular stuff. About a week after the transfer I noticed the leaves were taco-ing. I checked the pH again and it had crept up from around 5.8 - 6 to around 7. I added more pH down and another half week later the pH crept up again to around 7 and the new growth started showing interveinal chlorosis with black tips. The tips are not dead (yet ) but black!

If you recognize these symptoms, please do let me know what you did to fix it. I'm prepping to simply flush the existing reservoir and reset in hopes of eliminating whatever is messing with my girls.

what ppm do you use for your plants? you have to measure this in hydro
you can't let the pH drift so high. You should use softer water and hydroponic nutrients if you want it to balance itself automatically on 5.8. otherwise, you'll have to constantly check and adjust pH to keep between 5.6-6.2 max

PPM is around 1020. This isn't my first grow. . .Just first time seeing these symptoms.

What ended up happening is I adjusted pH again and waited two days. The black tips faded on two of three showing the signs and the plants look fine. Just a little interveinal chlorosis lingering.On the third of the three the black faded but the margins were left burnt where the black was. Otherwise it looks like she is coming around as well. Still unsure as to the source of the symptoms.

sounds like it'll happen again