Veg for another week or two and you should be on your way to an 8oz harvest with a plant that size. If the canopy grows to be 2.5 x 2.5ft or 3ft x 3ft then you should get the yield you're looking for.
However, (and please don't take this the wrong way) I wouldn't trigger flower just yet as there are a few problems I'm noticing that you should correct before flipping to 12/12. In veg, you can correct mistakes but come flower you're pretty much SOL if you mess something up as it will more than likely be irreversible.
The problem isn't just overwatering but mainly a lack of drainage for sure from what I'm seeing. Plants are droopy because the water you give them isn't draining, so your roots are literally drowning. What kind of container are you using? Looks like a cardboard box with a trash bag in it? How many drainage holes do you have in the bottom of the box/trash bag? And also, what kind of soil are you using? Almost looks like Miracle Gro but I don't want to assume
Again, not trying to be an ass, just trying to get a better idea of your situation because it's tough to give solid advice without much information.
And again, you're in veg so there is absolutely NO reason to panic. When you're in veg the only thing you can't repair is a dead plant, literally everything else can be fixed.
Here is what I would do if I was in your shoes and this was my tent/grow. Get yourself a smart pot
https://www.amazon.com/Handle-gallon-Flexible-Portable-Planter/dp/B00YHALNAK/ref=sr_1_5?ie=UTF8&qid=1513130048&sr=8-5&keywords=25+gallon+fabric+pot&th=1
Smart pots are some of the best pots you can get because they're made of fabric and thus are breathable, meaning your roots/soil will get more oxygen than if they were in any other container. If you are in fact using a box/trash bag currently then transplanting will be rather easy. Just fill part of the smart pot with soil, put the box on top of the soil, cut the box/bag with a box cutter and get rid of it. Then cover the now exposed root mass with new soil.
You absolutely need to transplant though in my personal opinion and for multiple reasons. For one, like I said above the smart pot will provide extra aeration/oxygen to the roots. For two, when you transplant get yourself some legit soil. Even just from that photo I can tell the soil is rather mediocre, I'm seeing more wood chips than I am perlite and that tells me the soil is poorly constructed. Are you near a hydro store or anywhere that you can get your hands on some good soil? The link above is for getting the smart pot, if you can afford it I highly recommend the 30g pot. Looks like you're in a 2ftx2ft tent and the 30g pot is the largest pot you can fit in the tent. The more soil you have, the bigger the plant and thus the bigger the yield. You already have roughly 11g of soil so I highly recommend the 30g pot, or even the 25g pot. After you get your fabric pot, get yourself some good soil. 1 cuft = 7.5g so I recommend getting yourself 2 cuft worth of legit soil and another 1/2 cuft of lava rocks. I recommend either Fox Farm or Roots Organic because they make some decent soil. Go down to your local hydro store and get a single bag of Fox Farm Happy Frog, it's a very balanced soil and isn't as hot compared to the Ocean Forest. A single bag of Happy Frog will run you around $15-20 at any hydro store, $35-40 on Amazon. Then after that you just need a single back of red lava rocks from your local home depot/lowes. Mix those two bags together and use that for your new soil mix, then transplant into the new pot/soil mix. You'll spend between $30-$60 on everything I listed, depending on where you get it from, but it will do wonders for your plant and it will be money VERY well spent. Let me put it this way, assuming you spend $60 on this it will pay for itself if it gets you an extra 1/2 oz or more of meds.
All the above being said though, your plant does in fact need a lot of help.. but shows a TON of potential. If you're willing to go through the trouble of transplanting into a legit pot with legit soil you will be one happy camper come harvest time. If you flower now, it looks like a 3-5oz plant simply because it's stressed because the soil isn't optimal for a variety of reasons. However, if you transplant it into a good pot/soil then you can damn near double your yield. If you take the time to get the plant transplanted and healthy you can easily pull a 1/2 lb from a plant that size. I've flowered plants that exact size and got anywhere between 8-16oz a plant, strain dependent of course.
Get that plant transplanted and back on track until it looks happy and healthy and you'll be incredibly stoked with your harvest for sure. That plant easily has the capability to yield 1/2 lb, hell if you scrog it and veg it for another couple of weeks you could even pull a pound from it if you use the full 600w from your light.
Give us some more information and we'll be able to give you much better advice because right now all I can do is assume. There are lots of helpful people on these forums and no one is here to belittle anyone for being new, it takes a real piece of shit to do that IMO. Get me some more information going and I'll help to the absolute best of my ability.