drooping plants, plants not doing good

short story, changed the water of dwc 2 days ago and plants just pooped over =(

temp70 humidity 60%
ph is 6.0
2 and a half gallons of tap water in 5 gallon bucket
ppm is 300
LED 20/4 lights(low light right now because of the stressed plants)
dual air pump
dynagrow nuts(using 1/4 m/l)was using a whole 1 ml but thats when the problems started
using sm 90 to clean res clean( has worked for 3 weeks, plants were flourishing and rapid growth)
total amount of time since started grow 4 1/2 weeks
i will say the roots recently look slightly tinted but no slime, no bad smells and they look whiter in the water

any input would be greatly appreciated, i'm certainly at whits end

Do your roots feel a little slimy?

Couple questions... What is your water temperature? Are you using softened tap water or hard water?

Also, I would lower your ph more around 5.6-5.8. Not sure how much light gets through that hole but consider raising the plant and reduce the hole size to avoid light penetration. And if the white plate is your only blocking for a larger hole at the top get some black covering to avoid light penetration (i.e. paint top black, black garbade bag, dark plastic lid, etc.)

-Jim

hey guys thanks for quick replies =) @jim thats whats under the plate. i have my black air tubes coming in from top so early on i added the plate to help with any extra light leaks, as far as i can tell there is no light leaks. @bugeye no the roots do not feel slimey(just checked)

how far from the light? what's the wattage? The one plant look pretty sick really for over a month old

you can trim off dead leaf parts to encourage new growth, maybe it can come back.

Assuming your water temp isn't the issue. I would suggest flushing. Remember to let your tap water sit out for a day (gallon jugs, bowls, etc) to evaporate majority chlorine in the water.. I'm assuming this is a pure single DWC system so your other plants are doing ok? Or purchase a couple gallons of 0ppm water from Walmart.

I'd start by checking your PPM directly again and your water temperature if you can. Then Flush clean. Are you able to drain all the water out? When do you test ppm?

thx for the replies guys, after more careful observation, i do suspect it is beginning of root rot...it just so hard sometimes to get the correct diagnosis

^bot?.....