strange Christmas lights with 50mm & E-5

Last Friday I wa in Bern, Switzerland, taking pictures of the Christmas lights. Back home on the PC analyzing the photos I saw something strange. All the photos taken with the 50mm Macro had a violet halo around the highlights (lamps). The lens had no filter mounted. Is this normal? It seems to especially be pronounced when underexposed (img #2). I know that the 50/2 suffers from chromatic aberrations but this seems to be a little extreme.

The images taken with the Leica Apo-Elmarit (no UV-Filter)

Nr. 1

Nr. 2 underexposed

Nr. 3 with Leica Apo-Elmarit (no UV-Filter)

Nr. 4 with 12-60mm (with UV-Filter)

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Courage is not the absence of fear; courage is the will to go on in the presence of fear.