If you notice any yellowish fungus/mold you are seeing in your jar, we do apologize. The good news is that this fungus/mold will not impact your plant growth -- it is a purely aesthetic problem. It does not affect the ability of the growing medium or product to function well from a plant performance perspective or from a consumption perspective - plant matter and fruit will be safe to eat, though please do refrain from eating anything other than your growing herbs! :)
That said, we're more than happy to offer you a replacement jar if you would feel more comfortable growing a new one. Simply share with us your mailing info and we'll have that out ASAP.