Hygrophila Corymbosa "Compacta"

Super healthy and lush. Sat in a bucket for 3 days before planting. Not a single snail!

I bought two pots of this plant with a bunch of others for my new 75g tank. All plants arrived in great condition but now that the tank has been planted for 2 weeks one of the Hygrophila Corymbosa Compacta has completely withered away. I expected some melt back as the plant adjusted to the tank which did happen but the thriving plant has already started getting taller and making lots of new leaves while the other is is still melting back. I’m still hoping the plant will bounce back but it’s not looking good.

When plant was shipped out to me, the stems were very minimal with little to no leaves. I put it in my tank with the adequate nutrients in order to revive it but in the past few days, the roots started turning black and the stems began to turn into mush (they would bend like paper). I for sure know there isn’t anything wrong with my water parameters, as my older hygrophilia corymbosa is thriving.