title_body: Why is my drip-coffee machine making watery coffee lately?
upvoted_answer: Well this is a strange problem but it seems to have to do with the new grinder you are using or the way you use it since the grind is the only variable that has changed (according to your story).
  
  Watery coffee most often means that you don't use enough ground coffee. Try using 6g of coffee per 100ml of water for a medium roast. If the roast is very light you may use a slightly higher coffee to water ratio. If it is not the quantity of coffee it is probably the grinder setting. Try a finer grind, something between table salt and sand (probably just the medium-fine setting on your grinder, however do check with your fingers). The problem may be what was suggested in the comments. If the grind is too coarse, the water is just running through the coffee and doesn't leave the time to spread and steep. This is in line with the hole in the center of the coffee bed you are describing. Maybe try to measure the time the coffee needs to run through and see if it changes if you grind finer.
  
  If this doesn't help then I'd suggest you properly clean the spout and make sure the water is dripping out the way it is supposed to. Maybe scale has built up which is channeling the water, forcing it through the spout in a stream that hits the coffee grounds with too much pressure.
  
  I suggest you try all of the above which will most likely solve your problem. Additionally however you could cut up some standard paper filters and place them on the ground coffee so that it is completely covered. In theory the water should then distribute much more evenly through the grounds. I'd suggest you do this only after you have solved the general problem as a means to improve the flavor. It'd definitely be a quite "hacky" solution and I think first of all your machine should work the way it is supposed to.