New NFT setup, and plant wilting during light cycle

Hey guys,
i've grown in soil before and this is my first NFT grow, so everything's a bit new still.

So got 2 different strains growing and the other one starts to wilt after sometime in light cycle.
I'm using 20/4 cycle and the wilting starts after around 12hours of light.
My pump has been 24/7 since there was enough roots in the rockwool cubes.

And as u can see it's only the one in front that's wilting.
I've been adjusting pH every 1-2days, depending how fast it was drifting from 5.8.
The pH has been drifting from 5.8 towards all the way to 5.1 with EC lowering just a touch.

So began to thought it was rootrot, but i dont know.. Atleast the roots i can see under the cover are all white and healthy looking.
Also if it were only the few last light hours i could put it on the strain or smth, but it's wilted for so big portion of the cycle.
What about stem rot? Or any other insight is appreaciated.




Thanks

Put your pump on a timer. Looks like overwatering to me

I'm 99.9% sure that the wilt is due to overwatering. You will need a cycle timer and it will need to be programmed to be ON for 1 minute per every five minutes OFF(on 1- off 5). You can purchase pre-programmed one for around $20 off of eBay. Easy peasy bro!

I agree with u guys that it definatly looks like overwatering.
It just seems weird to me that while the pump has been 24/7 on for some time, the plant looks very healthy during the beginning of the light cycle.
So is the the wilting lack of oxygen/(overwatering) ? Is that because the stem is rotting and can't keep up with the oxygen intake later in the day?

I could try tuning the timer on it, but it doesnt quite add up to my sense why the plant is acting that way.

Thanks for comments so far!

NFT does not require a timer, keep the pump running continuously
ensure the stream is shallow and flowing smoothly off the channel

the plants do not look wilted, often the leaves droop down which can look like wilting to the untrained eye, this happens after 15 hours of light
i call it the sleeping phase

wilting is caused by a lack of water this will cause the leaves and the stem to collapse
over watering is possible with hydro but this will cause yellowing and is very uncommon unless you have plants sitting in a puddle of water with no movement

its hard to see whats going on from your pictures can you take some better ones
without the hps

peace