3 month old feeding issues, HELP

Paulsaggiebride

My twin girls have always been great eaters.  They will be three months on Friday.

Lately, one of my girls will eat fine, but the minute you take the bottle out of her mouth to burp her, she wants nothing to do with it anymore. You REALLY have to work with her to get her to take the rest.  Part of me thinks she just isn't hungry, then another part over analyzes and thinks she is having trouble re-attaching to the bottle. 
Some bottles she eats the whole 5.5 ounces, while others we only get maybe 3 in her. 

Suggestions?