Hmm, seems suspicious that it happened right after the new pump was installed...
Something that is not all that well known outside of the plastic industry is that plastic parts can have an oily residue coating of a 'mold release agent'. This type of spray product facilitates the easier removal of the plastic piece from the metal mold. Typically, these are silicone based and not really harmful, but I have no idea what may have been used for this Jeboa pump's parts.
https://www.ehow.com/how_6595411_remove-release-residue-plastic-parts.html
Best practice is to always clean any new items added to an aquarium, just in case.