Please help diagnose my plants!

Hello all, this is my first post on here, as well as my first grow. I know I jumped into somewhat advanced waters (no pun intended) by choosing DWC as my first grow, but that's just the way I am.

Anyway, I have a small space to grow in. 5 feet tall, 4 feet wide, and 2 feet deep. Inside are two, 6-site DWC tubs that are homemade, a 400W HPS w/ 6in. air cooled hood. Each side of the hood has an 80cfm in-line fan. The room itself has one 80cfm fan pulling air in the bottom, and another pulling hot air out the top. The room stays at 78 degrees during the day and 70 at night (Fahrenheit).

The tubs have 8 gallons of RO water in them, with an airstone and aquarium heater in each one. The water stays 69.8 degrees F. The pH stays between 5.5 and 6.0. I am using Cyco Nutrients Grow A/B (NPK 6-4-4 combined), and supplemented with Cal-Mag. PPM reading of 550 (3 TBSP nutes, 70ml Cal-Mag).

I currently have 8 plants growing (all from clone). 2 Blue Dreams, 2 Jack Herer's, 2 Skywalker OG, 1 Casey Jones, and 1 Pandora's Box.

Below are some pictures of the problem plants( except for the healthy Blue Dream in the 3rd pic), I hope you all have some advice!

-Shaggy

Skywalker

Skywalker

Blue dream

Casey Jones

looks like nute burn. GL

Hi.

First off lower your water temp, it's way too warm, 60F is optimal or so I've read. I go by touch, cool to chilly.

N def maybe. And you probably will want to look into a water/root treatment like Pond-Zyme or HydroSparkle.

One last thing, air is kinda like light, it's hard to have too much. My water looks like it's boiling.

Good luck.

Tends to look like nute burn to me too.

Now all my plants have what looks to me like Mg def. How is that possible with 70ml of Cal-Mag in the water, along with my pH and water temps being constant? And it's NOT mites

flush with plain water no need to ph. then use tap water, or water with a decent starting ppm.

i susspect your problem is comming from the ro water.ive never used cyco nutes but im going to say there isnt enough micro nutes in the water.

because you are taking them out by ro, your plant is using the ones it receives from the bottle too fast.

leaving a shortage and in turn a lockout.

hope this makes sense....

also if your doing diff strains in the same 6 site dwc, bear in mind that they might all like different levels of food, this might explain why your blue dream is healthy (doesn't mind too much nutes, big commercial strain) and your others are feeling it.

i can feed slh up to 35ml in flower, my lemon skunk can only take 15mls,....

That totally makes sense about the Mg. Cyco has like 8 other bottles of additives but I only have the grow a/b. Would it be worth it to get some with more micronutes, or just go with a more well known and proven brand of nutes?

I am definitely going to mono-crop next time, and with fewer, but bigger plants.