I'd advise you to start by using only potting soil, mixed with some extra Perlite (an expanded rock product, available in bags at the garden center). This will help keep the mix open enough to allow drainage and air to the roots.
If you haven't already drilled drain holes in your buckets, maybe drill smaller holes, and more of them. Say 1/4in. holes instead of the great big ones you had. Then don't use the landscape fabric in the bottom of the buckets. I've had success with a single layer of newspaper - it 'filters' the water out and eventually rots away but by then the soil has compacted enough in the bottom part of the bucket to stay in there. But I also like to use the bridal veil netting I described above. You can even re-use your coffee filters if you use the paper ones.
Also, set the buckets up on something so you can see that they are draining properly. Soak the layers of soil as you fill the buckets, then let them drain until they stop dripping before you plant your new plants.
