Cloves and star anise contain certain essential oils (eugenol and anethole) that are chemically very similar to #6 (polystyrene). Because of this chemical similarity, these spices are able to melt the polystyrene.

A better choice would be to store the spices in plastics #2 (high-density polyethylene) or #5 (polypropylene).

The best choice would be to store these in glass containers not plastic.

Sources:
https://www.cooksillustrated.com/how_tos/11024-why-you-should-store-spices-in-glass
https://chemistry.stackexchange.com/questions/28430/how-do-cloves-break-down-plastic

per Google search using parameters "ground cloves melt plastic".

Best of luck.