Same buce from same pot in same tank, very different condition

[qoob]

Attached is an image of a buce I recently added to my tank in two parts on different sides of the tank. Both came from the same pot and were planted at the same time. The one that is doing better was super glued on a rock next to another buce that was on a different rock. The one that is doing worse was gently pushed into a hole between two rocks with another buce (so they both have the roots in the same hole). Before adding the buce there the older buce was also doing better, too.

Both sides of the tank get equal amount of light, and probably flow as well (can't really know for sure). All the plants around both of them are doing well.

What might cause this? How do I make it better? The same buce is doing great in 3 different spots of the tank, but not this one.

 

[Delapool]

Damaged roots taking time?

Other thought was if injected CO2 that could be uneven distribution depending on tank size.

 

[qoob]

You're probably right - checked the roots and they were kinda short and stuffed with rock wool. What I don't understand is why the older buce next to it started to melt. It was doing well before. They do have their roots in the same hole, but didn't think it would matter? Do I need to up my ferts?

Also no co2 yet, flow should be OK.