wilbur4321 First, yes there is a lot of stone in the Hard Areas. There is a total of 1579 stone in Pink Puma and a lot of it is in the Hard Area.
Second, there is a total of 100 Teal Tiger Diamonds. They are pretty easy to spot, so whatever you haven't gotten elsewhere is going to be in the Hard Areas. You have 27 more days at this point to finish the Event, so you should be able to get the rest in that time.
And you really should spend them on 1 Sitting Pink Tiger (the 98 Regen one) and 3 Furious Pink Tigers (the 130 Regen one). Both of those take up 2 slots each, so you aren't getting much in the way of Regen per slot, which is why you want to go with 3 of the 130 Regens.