Brown tips of two week old plants

Ok so im growing 4 plants that are now in 4 " rockwool cubes under 4 6500 k florescent tubes and 2 5000k tubes the lights are about a foot away right now. Have been watering with just water. I only have test strips for water but it was under 6.2 ph. I noticed the tips of a leaf or two on 2 plants have brownish tips and another plant has i couple spots on one leaf and the other one looks fine. I have been soaking the bottom half of the rockwool for 5 secs every 12 hrs. Temp is 24C. humidity is between 30-40%. \I have a fan blowing on low speed constantly and my lights are on 24 hrs /day. Then 4 days ago i start watering with 1/4 strength nutes. The plants are growing nicely and still and the brown is not getting any worse. Just up'd the nutes today to 1/2 strength. Im using flora series gro, macro, and bloom along with rapid start and florious plus. Any insight would be greatly appreciated. THX.
This one is a bit small then the rest but its a diff strand AK 48 i believe. some yellowing on the end
Growing nicely couple yellow tips. Northern light.
Couple spots in the middle of one leaf. Also northern lights
This ones a little small but doesnt seem to have any yellowing or browing
Any help would be greatly appreciated. Thx again

Peace my friend..... from the looks of it i would say lack of available nutrition.
mainly nitrogen(yellow leaf tips) and a little calcium deficiency(brown spots) . but by the look of your plants not all is lost this can be fixed.
First .. strips are good but can be some what a challenge to gauge so i suggest getting the general hydroponics test drops it comes with a vile and is extremely accurate also very cheap either just under or right about 10$. i suggest the drops because your ph was too off you want to aim for 5.8 this ph is ideal for seedlings up to mature plants in a hydroponic system and is very easy to gauge with the drops your looking for a goldish yellow color to a school bus yellow color this is 5.8-6.0 max and perfect. also because your in hydro you have to "charge" your medium in this case rockwool cubes with a weak nutrient solution even before you plant in them this is to assure your plant will have a supply when ever they run out of there natural reserve which can be small. i hope i have helped

Peace my Freind
K.D.

I have a digital ph meter and ppm meter coming just waiting on delivery thats why i got the test strips because thats all i could find. So your saying they are yellowing/browning because of an improper ph balance?

Half strength might be too strong for them at this stage, they are just starting to need nutrients at 2 weeks old. If in doubt, flush it out.

It sounds like you are over watering them too, I use a 10ml syringe to water with at that size giving them about 5ml each everyday or more if the cube is drying out too much. It's good to let it dry out a bit as it encourages the roots to look for water, soaking the cube every 12 hours is not so good.

It sounds like you are giving them too much love too soon! Good luck with your grow though and you'll find it much easier with a ph meter.

PH does not matter unless nutrients are involved. Ph affects nute uptake via the roots, not water uptake.

How do i flush out the rockwool?

I would find something like coco mat, or hydroton to elavate the cubes to keep from getting wet.
You're most likely experiencing a mild form of damping off due to rockwool staying wet.

Ok i have hydroton. Should i flush them still? If so how? I do have root show out the bottom of two of the 4" cubes. Should i got back to 1/4 strength nutes? And how do i hand water them when they are in the hydroton? I vid i watched used drippers but i could find anything for that set up around where i live s im hand watering

You need nutes. I would even pre-charge rockwool with around 150ppm(even more if your using tapwater and the ppm is already around 200. No more then 300).

When I started using inert mediums this keep happening at the begging and I kept reading that you SHOULDN'T give any nutes until is have x amount of nodes or is x weeks old. I'm calling bullshit. If I don't feel after that first single set of leaves comes out they do exactly what yours are doing. Feed them with a low ppm and ease them into it. Those leaves wont' recover but your new growth will really take off and look healthy. After I fed my plants that were doing that they thanked me.