I've never actually refilled one but I've heard it's good to put it on the washing machine when you've refilled it, that helps vibrate the carbon down so you can add more and make sure it's fully packed.
I heard the carbon bed on the ac infinity filters is not as deep as most, which makes sense...
When you flip you are changing the light hours to less and the dli changes.
Plus they are happier when they're transitioning and flowering under higher intensity than when vegging.
I'm only asking because I want to make sure you've enough light to do what you are trying to do.
You wouldn't be the first person or even the millionth to not be properly lit due to crappy light manufacturers sales blurbs.
As far as the rainbow kush, I've not grown it, but lots of seed...
Regarding your light.
The input power on the back is unlikely to be the actual power of the light, it's a marketing practice performed by shitty light companies.
So my question to you is, do you have a link or a name of the light?
What size area are you trying to grow in?
Have you checked all your autopots valves are seated right and all the silicone plugs are seated so they're square on so that they are working right?
Did you put two inch of hydroton in the bottom?
I'm not sure they still recommend that, but they certainly used to.
Do you have anything...
If you look at their refurbished rspec boards and their heat sinks you could build something for cheaper than there actually fixtures that would suit a 5x5 better, because tbh their lights aren't well spread , especially for 5x5 spaces.
I'd go with 3 triple hat sinks with 3 boards each and then...
I was under the impression it's a 3 part nutrients and you use all 3 parts through veg and flower.
So you'd need the grow.
Unless your using a different GH trio?
Have you looked at the feed charts?