lost 40% of buybox's and sales in last 2days

been on amazon for a few years now so no how things work but i have gone from selling £2400 daily to yesterday £1500 no changes that are big a few undercuts as normal...and some items out of stock waiting to hit....nothing big to cause this...

Looks like i have lost buy boxes for 40% off items

worst thing is i have just had 1 x a-z claim drop off my metric and 2 x negative feedback

any help what to check would be very helpful

as scratching my head about this...

items i sell are all year round no drop in sales

thanks