Leaves and roots !!!!!!

Check your PH, make sure it is between 5.8 and 6.2 . Your nutrient ppm should be around 800 at this stage. There needs to be about 1” of space between the bottom of your basket and the top of your reservoir. The water temp needs to stay around 70 degrees F. Use an inoculant like Hydroguard. I grow DWC and it is super easy, NOT expensive, and will produce just as good a bud as any other medium out there. If this doesn’t solve your immediate problem start looking at light distance, intensity, and VPD.

I doubt thats root rot.. its just dust from clay pebbles and maybe coloration from the nutrient solution. However your plant look like they dont like the water. Use half of the nutrient recommendation , very very few of ca mg if not not at all and if you use fulvic acid, use very very few until they get used to the hydroponic food. Make sure ph is okish. I personally dont do anymore dwc bcs, unless you have a 10000$ automated system or lots of time and nerves to spend its not worth it. Soil is best.

Wombat............ Typing an actual question doesn't cost anything!

You gotz the root rot. Main drivers of root rot is high reservoir temps, oxygen levels not high enough, light leaks in your reservoir, and contamination(aka wasn't clean to begin with). Hydroguard IS a great product and it works well. Unrelated but your reservoir also looks VERY full, like filled all the way to the bottom of your net cup. You want a little bit of a gap in between. I know it's tempting to overfill early on while waiting for roots to emerge but the bubbling action should mist your cup enough. In a 5 gallon bucket DWC I only use about 3 gallons of solution.

Make sure to keep Temps In a good range Make sure to keep hp in good range Fluctuating Temps amd ph can really affect a hydro plant more than soil plants Have you tried adding anything like hydrogaurd to the water things like that help keep the roots white I would also try to change out t the water in system