you don't need coords! As soon as you zone into PC, and you enter the actual cavern tunnel, with the mud burrowers, look around and in every group of mushrooms you see. Look for the Blue cap (see image) Click blue cap, receive Dulfis Mushroom
I have found four spawn spots for these shrooms, each with a respawn time of approx 13 mins. They are a nice, free way to get brewing to 88 making Murky Gray Liquid. Spawn spots are all in clumps of mushrooms, at:
-3837, -63 -3853, +285 -3570, +25 -3452, -220
There could be others, so check every clump of mushrooms you run across, but these are the only four I found in the area.
And you can also stock up on Muck Covered Hearts which drop off the crustacean-looking things while you're in paludal, for making Flarra's Soothing Tonic which trivials at 68. The hearts don't stack, and you need 2 per attempt, so bring empty bags with you.
I would find a bunch of these in Padual Caverns near the Shadewood Thicket zone line in the circles of mushrooms. Been wondering what they were for. Hope this helps