My DD has a brilliant day and then one or two "rubbish" days. This has always been the case since she was a baby. She would wake up for one day and then the following 2 days she would mostly be asleep.
It's the same now. One day she will be soooo interactive and engaged. I wouldn't have any concerns about her development at all. Then the next two days I have to work for eye contact/smiles/laughs/vocalisations.
Two days ago she was sat up on our bed practically copying us saying "hiya dada" and waving her hand about in a fashion, and the next two days she won't even look at me. Let alone entertain my babbling attempts.
Has anyone else had a similar pattern?