Does a lack of weight gain in first month delay milestones

[babydays12]

My son is coming up to 12 weeks and is missing a number of development milestones.

Eye contact
Tummy time head raises
Social smiling.

I know these are met a different times for babies and I'm trying not panic or anything but I wondered if failure to thrive in the first month can delay it.

He was born on 75th percentile but dropped to 5th percentile by week 8/9. He's slowly growing back up to speed (up on 9th percentile now and being bolstered by formula milk.

Is it known that babies like this develop more slowly? Should I be looking for the milestones a month later or something like that?

I've not heard of this but then I'm not a HCP.

That is a significant drop in Centiles though @babydays12.

If you're BFing are you getting any RL support and has he been checked for Tongue Tie?