Baby not putting hand in mouth while lying on back

[Db87]

My 15 week old DD is struggling a lot to put her hand in mouth while laying down. Sometimes she can take it but can’t keep it for more than a few seconds and getting extremely frustrated. She reached for hanging toys in playgym at 12 weeks and can even bring the toys close to her mouth. She has started teething and is extremely fussy to be not able to self soothe :( I am getting extremely worried as al other babies of her age are doing it already. Has anyone else experienced it?
Thanks

Babies develop at different levels. I wouldn't worry, she'll soon get the hang of it.

Thanks for the assurance @mishmased

Try not to worry. DS2 couldn't bring his hands together in front of him or in his mouth when lying down until 4.5 months. He was under physio and they weren't concerned.

Thanks @Foreverbaffled