I'm on ground floor apt 1B. Above me is apt 2J a different line than ours. They have a bathroom and a kitchen above my livingroom. There are pipes above the ceiling. I know as ceiling fell in the past. Landlord thinks it's
Apt 2J causing leaks. I think landlord is just stalling. What do you think?

Well what is his plan of attack. What has he told you he will do?

Its almost a not brainer that the bathroom/kitchen above you is leaking. The tenant may not be able to find this but the LL sure should. Once your ceiling is wet is should be opened and replaced. While its open the leaking will be easier to trace. You need to start hounding the LL to get this repaired. Wher do you live, you might be able to withhold rent in an escrow account until repairs are made.