Overwatering?

So I've had one small successful harvest so far, but am still pretty much a newb. Right now, I've got one bagseed plant growing in a rubbermaid type setup, which seems to be working ok. Only problem I see is the plant starts to droop after like 3-4 days of no water, and the soil is dry at the very top, but sufficiently wet only a couple inches down. When I water, she perks right up, but I'm kinda of scared to water her every 3 days, because last time I overwatered and it was a mess. If the soil is still damp 3 inches down when she starts to droop, am I overwatering? I usually water with about 800mL so that it barely runs out the bottom of the pot each time. Might the drooping be lack of nutrients or is she just a thirsty girl?

nope man, thats about right, i water till some comes out the bottom, dont water again for at least 2 days, i have a 5 liter pot so its not too big, i have to water more. but if the soil is dry for the first 2 inches its time to water, yet alone 3, when it droops like that, that long after watering, its because it needs water, i watch my plant, once it starts to droop just a tad i know its the right time to water. this is usualy every 2-3 days, depending on what time of day i water.

Awesome, thanks a bunch man.

any time