Yeah, that's most likely too much watering, but I doubt that's the only thing causing the leaves to droop. When I first plant a tree, I water it roughly every 3 days with a deep watering for the first 3-4 weeks. Make sure the soil drains pretty fast if you're gonna do it every 3 days though (water shouldn't pool on the surface for more than 30-45 mins after the water is off). Then depending on the season, I cut back some.

There might be more than 1 issue here though if it's already having problems. The soil might need some amending, or you planted it too deep. When I first started planting trees I didn't know that deep planting hurts trees as much as it does.. Now when I plant a new tree, I create a sort of "plateau" of higher ground around the tree (only 1-2 inches higher than the surrounding ground), and then with a berm around the plateau. Then on top of that, I plant it so the first root (or root crown) on the tree is barely visible above the ground. It's much better to err on the high side when you plant a tree (although you definitely don't want it too high either). If the root system is still pretty small, or if it's in a windy area you'll want to use stakes to keep it upright.

If it is too deep, you can still easily fix it by replanting it. I fixed my White Sapote 1 month after I planted it. I could tell something was wrong the week after I planted it and now it's one of the faster growing trees in my yard.

Sometimes you want to check if they added soil to the container it's in. I've seen nurseries add soil for whatever reason (probably to keep the tree upright) and then we thought the soil line of the container was where the soil line should be in the ground (and we were wrong).