Nutrient strength

I am trying to get my nutrient solution dialed in. My roots are browning, so I order some hydroguard and will do a res change today. I'm thinking of setting it at 400PPM. Any thoughts?

Please feel free to give input on anything else you may notice. New grower.

BTW I have a DWC setup. growing in a 2X2.5 tent using a 200W light. Will ioncrease to 400W for flower.

Anyone?

What nutrients are you using? Are they brown?