No luck this past memorial day weekend

Hi guys, I'm kinda new to bass fishing, just got really serious about it a year ago. I've read many books on bass fishing. I watch all the fishing shows. I've even got subscribtions to Bassmaster magazine, In-fisherman, and Bassin. I live in Southern Maryland and this past holiday weekend I did alot of fishing from the bank and from my small basstender boat with trolling motor. I used numerous artificial baits to include spinnerbaits, crankbaits, texas rigged worms, and buzzbaits. I used various presentations for each of these with no luck. I fished near cover, in coves, points, deepwater, lillypads, and near the piers.The temperature had been pretty consistent the week prior with temperatures in the 70's. Not sure what the water temps were though. I fished on Sat. June 28th and Sun. Jun. 29th. Water clarity was kind of murky for whatever place I fished at. This was the worst for fishing for myself in a longtime. Two days prior to Saturday a slight cold front did come through which brought some rain. I'm sure that many of you have had days like this right? Do you think it was because of the cold front or the fact that the bass are at post-spawn or both? Do you think I would fair better with an economical fish finder? Talk about frustrating, please advise!! ??? ???