I'm sorry to hear about the issue that you're experiencing. The weatherproof materials for inkjet printing feature a special topcoat that is designed to absorb ink and protect it from moisture. The absorbent nature of the topcoat can also make it somewhat susceptible to environmental factors. Being stored in proximity to essential oils, chemicals, or solutions featuring strong fragrances can sometimes permeate the absorbent topcoat and cause yellowing over time.
Sealing or laminating the printed labels will typically resolve this type of issue. Under similar circumstances, some users choose to apply a clear protectant spray to their labels. Krylon makes a series of clear protectant sprays that are commonly used for sealing and protecting artwork, but there are other manufacturers of these types of sprays as well. You should be able to locate these products through online retailers like Amazon, or by visiting local craft and hobby stores. Applying a clear glossy label on top of the printed label as a sort of laminate is another popular option for adding durability to environmental factors. Both methods are detailed in the "Add Durability" section of the guide linked to below:
https://www.onlinelabels.com/articles/how-to-make-labels-waterproofIn the future, if you're ever in the market for a new printer you may want to consider a laser model. Since laser printers use a dry, powder-based toner for printing, the weatherproof materials don't feature the same type of absorbent topcoat intended to absorb and protect liquid ink. The lack of the absorbent topcoat makes those materials more resistant to the different types of environmental factors mentioned above. There's no need to rush out a buy a new printer, as sealing the inkjet printed labels should improve the results, but it's just something to keep in mind when considering new equipment in the future.
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