We have a two story house with two bathrooms upstairs. A month ago one tub wasn't draining and then a sudden noise and the water drained, coming out in the kitchen through the ceiling. We called a plumber but he couldn't find the leak. We have a big hole in the kitchen ceiling and we did use the tub, the toilet and the sink in this bathroom for a whole month and no leaks until now.
The tub again wouldn't drain and if then very slow and the water came down in the kitchen again. My husband said he thinks it is coming out where the toilet is, but I didn't really see it. A few minutes later we discovered that both toilets upstairs were clogged, we did unclog them, flushed a few times but no water coming down.
What could be the reason for the leak and where is it?
Does it have anything to do with pressure?
I hope someone can help us.

I think hubby is correct. Tub would drain into toilet lateral.
If toilet lateral or stack is blocked or partially blocked water the tub would not drain. If wax ring of toilet is missing or defective tub water would back up and come out between the toilet and the floor flange. It would then leak down to ceiling below.
If toilet blockage is cleared then everything would drain without leaking until toilet blocked again.
Remove toilet, snake line to insure that there is no partial blockage. Take note of condition of wax ring after pulling toilet. Replace wax ring and reinstall toilet.

If you related all this to plumber, don't engage his services again.

Thank you so much for replying so quick. I did ask another plumber and he was also coming up with something in the tub, then toilets then this and just couldn't figure it out. The way you described it, it could be the solution. Thank You!!

In the mean time you should try to determine what and who is periodically stopping up the toilet.

I had a second plumber come and take a look and that's what he found out, it is the toilet...
I guess it was either my daughter 15months old or my husband LOL