Newbie LED, Coco, Autoflower grow from WA

Hi everyone, I haven't been able to confirm my account for the past couple of weeks so I've been lurking in the indoor and LED forums. Anyway, now I am registered and can start bothering everyone with stupid questions (jk).

I'm starting a grow in a 4x4 tent with 8 freebie auto flower seeds that I got with an order from Seedsman. Growing in Coco Coir mixed with 30% perlite using Canna a+b and maybe rhizotonic (expensive...worth it?) They will be under a DIY 400watt LED fixture 4 Vero 29's (69v, 3000K, 90CRI) with 2 1400mA drivers. I might add another light if my budget allows for flowering as I know the one will not be ideal if the plants fill the space.

See you around

RIU has some great people here with tons of experience!! Im on my first grow and have been asking questions since day 1 and have received nothing but great advice. Happy growing!!