It's normal for this to happen and there's no problem, brother. The ones that are yellowing are the first fan leaves (just three blades), and that happens because they're at the base of the grow, and usually, the strength of the grow goes to the top, so in the lower areas, the older leaves turn yellow and end up not being necessary. It's better... you should just remove them since they don't contribute anything significant in terms of plant development, and all they do is disperse the energy for growth in the upper areas. Don't rush with it, and removing them is the way to go. Other than that, the grow is perfect in its development. Keep it up, brother.