Hi
I have transplanted some Lupins which are actively growing, I know this in itself is a mistake but they had very little room.

After potting in fresh soil with horticultural grit, the leaves on many of the big stems have started turning brown and dying off as pictured.

The plant is still growing well, however should I be concerned about it getting worse? Could it be a fungal issue or is it likely to be just from where some roots could have been damaged from transfer ?

Thanks