Charcoal and wood ash both will raise a mediums pH, not lower it.if u have any charcoal, use the ashes to drop the ph in the soil
Charcoal and wood ash both will raise a mediums pH, not lower it.
And the OPs original problem looks much more like phsical heat damage rather than nute burn. Nute burn is generally more symmetric in its damage. His issue looks to be localized on one side of the plant. Not sure if flushing is needed. Just get the light bulb a bit farther from the plant.
Also I hope he does not plan on flowering under the sink. Those areas are usually very damp and prone to mold issues.