This is the 2nd time this has happened - I thought I had solved it after the first by adding vinegar to my buttercream. It seams to only happen on colors cakes. I've attached a pic of the cracks I'm getting. It seems to only happen on the large tiers - 10" or above - mainly the 12 and 14" tiers, but a little on the 10. I also doubled up on cardboard rounds this time - along with then putting them on the plastic separator plates. I'm just not sure how to prevent this from happening again.... they're almost impossible to fix... what do you think?

They look like stress cracks. I don't know how many dowels you place in your cakes, could be it or does it only happen when you pick them up? If so it would be not enough support.

I use the bakery crafts setup system - 4 plastic dowels and a plastic separator plate - do i need additional doweling???

If you tried the vinegar and the boards the only thing it could be is the dowels, maybe your cutting them too short? Or not enough of them? I dowel to death, I would put like 8 around and 4 in the middle of the bottom. It's a lovely cake!!!!!!!!! The colors are striking, Keep trying and don't give up. I want to be able to afford those stress free cake systems one day myself. Though I can't really see anything bad with this cake, but I don't have my glasses on. Keep baking and don't give up!!!!!!

Yeah four dowels on that large of cake maybe isn't enough??????????????

I would say your problem is coming from letting each tier rest directly on the top of the other. Even when using dowls, if you cut them too short, or cut them level with the cake, you run the risk of the next layer sinking in juuuusssstt enough to put weight on the one below it. Try cutting your dowls about 1/16 or 1/8th of an inch higher than the top of your bottom tiers. Then, when you put the next one on top of it, it will have a very tiny gap between tiers that will keep your tiers from pushing down and causing cracks. I beat myself up for ever on this very subject until my Mom saw it and was like, "Are you leaving a space between plates?" I guess that's why SHE was the teacher, and I, the student. If you're worried about the tiers not staying in place, put some BC 'glue' under your plates to minimize sliding. Vinegar???? Eewwww....

I agree that they look like stress cracks. The only thing that I have found that solves this is putting the cakes on a wooden base, so there is no "give" at all when the cakes are moved. I think just the plastic separator plates alone would not give you enough strength, especially because your cake has so many layers. My husband bought a sheet of plywood (1/4" thick, I think) from Home Depot and cut out several different shapes and sizes for me to use. It was pretty inexpensive. I cover each board with contact paper and then fanci foil. I need to get these returned when someone orders a cake from me, but most people are good about returning them.

Hope that helps! (P.S. Pretty cake, by the way!)