Do this, add more CO2 and direct it at the Plant with some current, CO2 mist particularly.

Add the PO4, KNO3, TMG, GH booster at standard EI levels.
(you can do the PMDD style like I suggested on the EI thread and dose it daily via liquid)

Check your KH also, it might have gone up.

Direct the CO2 mist right at the plant.

That will ensure good CO2 and nutrients.

Then wait about a week or so.
It should grow back.

Regards,
Tom Barr