1 year old 5 gallon ready to add plants. help!

Hey guys, enjoy the website and the threads here. I have a 5 gallon tank in my office at work. It is slightly overstocked. I have 7 fish. The tank is a Regent AquaTech kit you can get at Walmart. I've doctered it up to look pretty nice with real driftwood and some riverstones. Anyway, I would like to plant it to really set it off. However my water changes from a yellowish haze to darker after a week of a 90% water change. Not sure what is causing that, I do not provide a whole lot of light and algea is not in abundance on the glass. My question is where do I start with my planting and what is causing the yellowish haze? Is it overstocked. I feed a small pinch in the morning. Fish have been healther and have had them for about a year now. Snails do not do well in my tank though. I've also noticed PH problems on occasion. I know this is a lot of info with not much specifics but any help would be great. Thanks

I thought about the driftwood too, but the driftwood has been in there for a while with no problems. It seems after everywater change the haze comes back quicker. The 90% is done whenever the water gets so bad other people notice. Here lately every couple of weeks. I have 2 zebra danio's two glowlights two head and taillights and 1 lonely neon. I clean the gravel when doing the water change when I replenish the water everything looks nice and clear for a week then back to haze. I have never been able to get the PH in my tank down. Guys I didn't mean for this to turn into a troubleshooting scheme, but I want to make sure my tank is ready for some green beauty.