There's a weird phenomenon going on with Finnex Ray 2 and FugeRay's (and I suspect with other all white LEDs) when it comes to red plants. There's been numerous complaints (mine included) that they tend to fade red plants to green... in the case of AR mini = more bronze. That's why, for while now, you'll see Ray 2 owners who have red plants complain and ultimately solve their issue by adding a MonsterRay. That is before the Planted+ came out.
CO2 does play a crucial role, too. But ever since I switched to LED's that supplement red light, my reds overall, got better. I don't get it either because 'they say' that red plants 'reflect' red and absorb blue light -- that's why they appear red. But maybe it's like the equivalent of us getting a tan to reflect certain rays of the sun? Maybe red plants develop more red (anthocyanin) when red light is present so that they can more efficiently absorb other wavelengths?
So... I have determined, that my AR mini is doing so much better in my 60p (14" tall) with Sat+ lights (x2 ~medium light) versus how they are doing in my super shallow 60f w/ a Ray 2 suspended over it (~high light). Both CO2 injected... both PPS-Pro. However, there are some differences that may account for this. My 60p has new Aqua Soil (although it's Africana and known to not be as fortified as Amazonia), I also dose extra chelated Fe, and my 60F is on DIY co2 + Glut at the moment because my CO2 paintball tank ran out. I'm going to get them refilled today and go back on pressurized. I'll see if the AR mini improves. If it doesn't than it's not the co2 and has to do with light (spectrum?) and substrate (nutrients?)... maybe Iron too (although some people discredit Iron as a means to achieve better reds)?
Ahh... the experiments we go through!