In my experience, MC is not a very demanding plant. I propagated an initial batch I got 3 years ago to various tanks and even sold some. I grew it in high tech high light tanks and low tech, lowlight tanks as well. Currently I have a large clump sitting in a bucket waiting to be transferred to a new tank. One thing I did different from you is that I did a dry start with the initial tank. This enabled strong root growth so that when I flooded it, it had a lot more to draw from while it adjusted to my water parameters. I am not sure whether you have the ability to do a dry start in another small tank and transfer from there. One more advice would be to lower your light brightness. In my tank that has the Twinstar 600, I find that it suffers at full brightness until it has taken full root. I use Tropica Specialized as well by the way. In my 20 gallon tank I use 6 pumps per week and the Monte Carlo is quite healthy.