Ok.. from the crash reports it doesn't appear it's Logic that is the cause of your crashes but something else you are using or have installed that is at the root of the issue..
Unfortunately you are currently using the five or six most likely external causes of such crashes in Logic... related to Yosemite... all in one project. Its like the perfect storm so to speak...
1) You are using an Audio Router (Jack in your case) These are known to cause issues with other Audio drivers when used with a DAW such as Logic and also with OS X after recent updates.. Uninstall it would be my recommendation.
2) At the moment, the latest version of Kontakt 5 is a little unstable and we are waiting on a further update from NI to resolve thiese instability issues...
3) Melodyne is currently known to have issues under the latest Yosemite. Again hopefully an update will be forthcoming to Melo...
4) Izotope Alloy2.. can also be unstable at times... and once more, a further update is probably needed to Alloy2 to resolve any instability issues...
5) Elastik can be unstable too..
5) RealRick is a new plugin that is known to be a little buggy at this time..
As to which of the above is the most likely culprit is hard to say though I would go for both Jack and Melodyne with Alloy2 a close second...
To trouble shoot and test..
Remove/uninstall Jack...
Create a new project and just use Logic's Built in plugins and see if you can recreate any crashes that way...
if al. is okay then add a couple of K6 tracks... and test again..
Now add each of the other likely culprits as i listed above.. one at a time and see what if anything causes the crashes...
Hopefully it was just Jack Router .. which wouldn't surprise me...