First hydro dutch bucket help my babies from dying

so i am a complete beginner with hydro,

i have a recirculating dutch (bato bucket) homemade setup. 400w hps for veg and flower

i have started my babies in rockwool starter cubbes and they are now transfered into the hydroton 11ltr buckets with a drip feed.

its been about 2 weeks since they sprouted and they have very slow growth and tiny leaves some yellowing very droopy, dying almost.

i will be using canna vega and flores nutes

please can some one point me in the right direction to get these babes going. like ec ph for first month of growth ? how often to change res ideal temperatures for water ?

so far i have only been using water to feed

Ph should be at about 5.5-6.5 ec should be super low at the beginning. I would not introduce nutes for the first 2 weeks. Res should be changed weekly or bi-weekly. water temp should be at about 70F. And when using rockwool cubes you should soak them in a ph balanced solution for at leat 5 hours. A lot of people will tell you to do it overnight but I never do. 5 hours is plenty. Good Luck Dude