Parents left blue tit nest

Hello,  I just wanted some advice as I have a blue tit nest with 8 chicks in my garden.  They must be around 2 weeks old and I have loved watching the parents work so hard to feed them constantly in and out working as a team. I have put out lots of food on my bird table to help and tried to not use my garden as much where this is near to my patio. This morning I woke to a devastating sight of what looked like blue tit feathers plucked all on the floor near to the bird box but no body. I believe one of the parents has been killed. I was worried the nest had been abandoned as I could hear the chicks still inside. An hour later at 9:30am I saw the other adult with food in her mouth but looked very on the edge and was not seen again. It has now been 10 hours and have seen no sign of the parent and the chicks have been making noises (very loud) for 10 hours now straight so they must be hungry. Has the other parent abandoned the nest?  Should I take them to my local wildlife bird centre?  I know I shouldn’t intervene but they are so nearly ready to fledge and I’m concerned the other blue tit has also been killed or left . It is heartbreaking and I feel the extra food I had put out may of attracted other birds/predators to my garden and feel so much guilt. Thank you