So slimeballs will only drop from natural spawned clay, if you place the clay they wont drop. im just wondering if it is supposed to be like this. If so this is a horribly annoying feature.
That is supposed to be so, its part of MCMMO to avoid people infinitely grinding levels and such. MCMMO detects if a player placed a block, and it will not yield exp if it was. (Exception of course being crops, as the growth resets this flag) That is also why you will not get battle skill levels from spawner mobs (swords, axes, fists, archery) However, you can still find plenty of clay naturally, especially if you have water donation perks to allow you to use sponges at the bottom of the ocean.