Are your sales actually lower, or does the site just say they are?
I will say this: be careful! Editing seems to be buggy. Make sure to re-check your description when you edit images. If you delete the primary, be prepared to edit a few times - your new images won’t ‘stick’. I don’t think it lowers sales per say, I think it’s at least partially a byproduct of the fact that the indexing system has to reread you Gig when you edit it, and the indexer doesn’t run in real time (they usually don’t). If you edit too much, the site will be trying to play catch-up to your edits. Your Gig will show up less because it’s still ‘deciding’ when to display it, more or less.
I have actually had no sales, but my stats bounce around a lot. Someone may be working on the statistics.
My recommendation would be to keep your own records of your sales, and see if you notice a change in the number of orders. Then look around in that category and see if there are more Gigs in it, or more similar Gigs, or if orders appear to be less across the category/subcategory, etc. Basically, keep track of what you think is relevant.