This can happen while they are teething, which lasts about six months.
Search this topic on YorkieTalk, there are a ton of threads.
*I have given a spoonful of cottage cheese daily to help with the calcium loss of teething.
*Massage the ears daily, helping the blood circulate
*I taped one of my yorkies ears on and off for 4 months...but pleaase make sure you know what your doing...there is a link on YT somewhere, you can ask your vet to do it.
Your baby is going to be perfect with or without standing ears!
Congrats!!!