If your municipality uses chlorine, my guess would be that it's about a 99% chance that's it. I built a filter system for my water, using a 2.5 x 10 inch filter housing and getting a solid block carbon filter to go inside of it. This was for ease as I'm already buying 5 gallons a week of R/O water for the house to drink and didn't want to deal with another 5-10 gallons a week, but this could be an option for you.
Basically, everything is available at Home Depot or any other hardware store for the filter system. It made a huge difference in the quality of my beer and sounds similar to the situation you are in. There was just this odd flavor to the first couple of beers I made, it wasn't bad, it wasn't sour, there was just this lasting after taste that wasn't quite right.
My suggestion would be, on your next brew, to buy "Purified" water from the store and use that. It would be a good starting point to at least see if the tap water was the issue. If the taste isn't there on that brew, then you know Chlorine was probably the problem. If not, then we would have to dig deeper.
Your temps seem fine, if that was actual fermentation temp and not room temp. Don't forget, fermentation is an exothermic process. So just because the room is 70, doesn't meant the beer is fermenting at that, it's probably closer to 75 or so. I tend to shoot for mid 60s with ales.
But as I said, I think first step is getting water without chlorine and go from there. There are other issues with extracts though as well. Make sure heat is off when adding them to the boil. Make sure they are completely dissolved before turning the heat back on. If it's liquid extract, try adding half at the start of the boil, then the rest with about 15 minutes left.
Sorry, yes, I did ramble a ton, but those are the first steps to try and I think you'll notice a huge difference on the next batch.