This question is asked almost daily, and with so many sellers with very diverse inventory you will likely find some that are also experiencing slow sales right now. However, the majority of sellers will differ from your experience.
Maybe your items do better in the warmer months? Or maybe your best selling items have sold out and what is remaining is lower demand products? Maybe your product offerings have more competitive products to compete with, or more sellers have appeared on the product pages your selling? Are your items likely to have newer versions and those newer versions are now available? Were you doing any marketing that recently stopped? How about your competitor products, are they doing marketing that is driving your sells elsewhere? Have you modified any of the product page (i.e. keywords, target audience, any demographic updates/changes)? Have you confirmed that no other sellers or Amazon have made any of these changes?
If you marketing toys and gift-able products, it is not uncommon to have a lull before the holiday season begins.
Unless your willing to provide additional information, what other sellers are experiencing — even if the same as you — maybe not be caused by the same circumstances.