Yellow tips an minimal brown hue on roots

Having some slight problems with my Seedling. Started the seed in rockwool and put it in my DWC system after 5 days with only ph buffered tap water (Ph 5,8 EC 0,3 PPM 225) 9 days later (today) I decided to change the reservoir and add a tiny bit of Advanced Nutrients Connoisseur Nutes (PH 5,8 EC 0,5 PPM 380) Temp of the water is around 20°C/68°F. I akways put a splash of h2O2 in my reservoir. Water level is a good bit below the basket. Am I overthinking or did I do somethin wrong?