On my first inspection in March I was somewhat surprised to find the quantity of capped brood - 4 frames 90% capped - my second season Queen is certainly one I need to look after. So when we had a cold snap I decided to replace fondant with a Rapid Feeder with thin syrup (1kg sugar, 1.25ltr water), but the problem I find is that 30+ bees drown 
The ‘inside’ ‘cup’ isn’t smooth - there are tiny steps, sufficient for bees to walk up. Could the bees simply be drowning because of the weight of their colleagues also trying to get at the syrup ? Is 30 acceptable collateral ?
It was a lovely sunny day today and a lot of bees were out foraging. Although there was still 1" of syrup in the feeder I decided to remove it because only 1 bee was taking any interest. Previously the bees extract every last drop of syrup from the feeder to the point where they’ll still be trying long after the syrup has been used up. Any thoughts on what is going on, gratefully received.
Yes. About 1% of a great queen’s daily egg production. Totally acceptable.
You have a nectar flow going on. Bees only take syrup when there isn’t enough nectar. Lucky you! 
Cut the top off a sports sock and put it over the centre of your rapid feeder making sure its touching the base.
The sugar syrup will soak into and up the fabric reducing the need for the bees to go down to the base.
I had the same issue and @FrederickDunn posted this solution on his YouTube channel.
Very few bees dead in my feeder now.
I’m not sure that I’d be happy to accept 30 drowned bees in a feeder, I’d be trying to avoid any drowned bees by using a different feeder. Maybe a baggie feeder would eliminate drowned bees. Another alternative would be an inverted pale with small holes in the lid, something like @VinoFarm uses, or used to use.
Also be aware that bees have all night to take syrup, while they can’t forage for nectar.