Super Silver Haze- First Grow Ever😅

I removed one plant that was not growing. Upon further inspection the root was yellow and hadn’t really grown since I put it in the Rockwool. The 3 that remain seem decent expect for #3 seems slower than the other but hopefully it catches up. I changed the buckets water for the first time and added the first round of nutrients. I have never used any fertilisers before so I’m not fully sure I’m doing it correct. When I first read the bottle i read 0.5ml of each nute, so that’s what I did. But I’m just realising it was probably 0.5ml/L…🤦 I’ll go back and check again tonight. I’m leaving 5 mins between each nute to let them dissolve and then adding ph down at the end. I also just bought “Southern AG Garden Friendly Fungicide” to help roots if they get root rot. Not sure if I can use this throughout the whole grow or if it’s only necessary when root rot is present? Also is there any other additional fertiliser I should be adding, like cal/mag? If there’s any other things I should be looking out for please let me know. I appreciate the feedback.😀