I agree, fm1234
Sunday and Thursdays are always best for me... and I believe we probably sell on the same local marketplace :)
It's really no surprise to me that Monday, Tuesday and Wednesday are slow for some sellers: They are slow days for a lot of businesses, epsicially ones who deal direct with consumers.
Restaurants, movie theaters and brick and mortar retail stores all see a slow down on these days. Most of them overcome the slow down by having specials on those days.
Who hasn't bought a cheap pizza or movie ticket on a Tuesday? They are certainly popular where I live!
Perhaps you could think about doing something similar.