Meaning of 'should have' in sentences

What is the meaning of 'should have' in the following sentences:

1. 
   

   I should have let her know what was happening but I forgot.

   
   


2. 
   

   They should have remembered that their guests don't eat meat meat.

   
   


3. 
   
   

   I should have sent everybody a reminded by email.

   
   


4. 
   

   He should have told them the truth but he didn't.

   
   


5. 
   

   I don't think you should have done it.

   
   

I'm confused here because I know that 'should have' is used to imply 'regret' for example:

1. 
   

   I got really wet today while going to market. I should have taken an umbrella.

   
   


2. 
   

   She wept so badly. I shouldn't have scolded her.

   
   

do the first five examples imply 'regret'? Or, do 'should have' implies both 'obligation and regreats' in all those 5 examples? Or, Do 'should have' implies both 'obligation and regreats' in all those 5 examples?