Wrong type of Joint Compound or Tape
Next time, tapered edges go together as much as possible.
As for the mud, all purpose (green lid from USG) can be used with paper tape. Mesh tape should be used with "hot mud" (the powder stuff in bags that needs to be mixed with varying dry times).
If you used the lightweight compound, which is a finishing mud, with the initial bed coat, you could definitely run into problems, not only with your mesh but also with your paper corners. It doesn't have the glue type additives that are essential when taping. Again, most of the work is done so you could let it ride and see what happens.
My biggest concern now would be the seams. On the butt side you are definitely going to have to float out moreso than if you had 2 tapered edges, probably almost 2 feet. It is all going to depend on the level of finish you are looking for.
Hope this helps.