My guess is your lake is experiencing a seasonable late evening or night bite...this occurs on most shallow lakes from Mid Fall into Winter. This means a day bite for the most part is very difficult and sometimes you haft to give them what they want...And right now for you is to fish at night.

I have dealt with several shallow lakes and from what you are saying the deepest water is 6 feet. Whenever your dealing with this shallow of a lake remember shade and cover become even more of a factor, and fish tend to become even more spookier.

If day fishing is all you can do right now try getting as deep into the dark'est shade you can find.... be it under docks or next to big live cypress or lay downs.
You must get your baits way back up under those docks in the daytime. This may mean sticking a jig pole way up under a dock with six inches of space from the water. With your non rod hand hold a little line so you can pull the trigger when you feel that thump as you wont be able to set the hook well. Being able to give your line a quick tug and setting the hook from a side ways motion under the dock will help you keep the fish buttoned up and get him out from underneath those tight areas. You can also try dock shooting the deepest docks or you can find or try a slip bobber and jig rig, keep your slip bobber close to your jig with a small split shot, this will enable you to pitch your bait way back under those docks, under tree limbs, or back into deep shady pockets with a bobber and enable you to give those spooky fish a nice slow, calm and steady offering. if you have allot of trees they will most always be on the wind leeward shade covered side, or in the tightest darkest pockets of trees you can find.

With all the recent cold nights we have had... sometimes they will fool ya and be on the sunny side basking in the warmth of the sun as it hits the tree trunk, so I would encourage you to try the sunny side of the tress also right now.

If you are trolling try your best to lay off the trolling motor as much as possible and use the longest trolling rods you can find to get the baits away from the boat as mush as possible. When trolling Oxbows make sure your covering the water column until you find what depth they are in, my guess right now... they will be on the bottom but they could also be a foot deep. Lastly when trolling look at your lake and how the sun throws shade over it in the mornings and evenings. Start your trolling efforts there where the shade lays across the lake the longest.

Keep trying the same bait you are using to catch them at night, chances are you will eventually find some day feeders that will hit it. If that don't work keep trying as many different baits as you can, starting with the ones you have the most confidence in. Remember stay the course... if you are catching nice fish at night, there are fish to be caught during the day. Good Luck.