Swimming toward the powerhead can be a symptom of gill infestation by parasites. Could be flukes, ich, velvet. So need to watch for other symptoms like hiding from light, loss of appetite, white spots, lethargy, color loss.
A freshwater dip is usually a good diagnostic to confirm or eliminate flukes from the equation. Some puffers do not do well when handled. Do you have a perforated scoop instead of a net to handle your fish?
To lower the puffer's stress, I'd probably consider skipping the FW dip and placing the puffer into a QT and treat with General Cure instead. As it contains both prazi and metro that will treat both flukes and internal parasites. Dose and then wait 5-7 days. Do a 25% water change and re dose. Wait 5-7 days. Do a 25% water change. Run carbon to remove any remaining meds and then observe for 10-14 days. Sometimes when treating with GC, the metro will cause the fish to reduce eating.
Very important: add oxygen to the tank when treating with any meds. A powerhead aimed up at the surface where it is actively rippling the water's surface will provide the best O2 exchange/addition.
All treatment come with risk. You never know how an individual fish is going to react.
