iPhone battery health dropping fast

The ageing process is not linear as the phone needs to recalculate. Possible this was at the end of such a calculation.

Ageing by 1% per month is not abnormal so a 6 month old phone with 94% health is perfectly normal

Have it replaced at 80%

Battery Repair

iPhone Battery & Power Repair

Change it when it gets to 80%.

If it gets there inside 12 months contact Apple Support

Depending on your region, you may be able to reach them here: contact Apple Support 

I know nothing about Airplay or Apple TV

Copy and paste your question into s new discussion in https://discussions.apple.com/community/appletv

Change it when it gets to 80%