Right: food! A few ideas. Firstly, do you find that you worry a lot if they don't eat what you consider a decent amount every mealtime, and that's why you cater for different tastes? If so, they can definitely survive if they eat nothing at any given meal, so brace yourself and serve up exactly the same thing for them both - something that's easy for you to prepare!
Say it all goes in the bin because they refuse it (both of them). It makes them hungrier for the next one, which is when you play hardball - another meal that is convenient for you and does not pander to their oddities. They'll eat some of it.
You can always supplement the second meal with a yogurt for pudding or something (assuming they eat yogurt or something quite healthy). But stick to your guns and don't let them eat any more between meals than usual.
I told you once before that I was a fussy child and am still pretty difficult actually. It's not good for anyone to be allowed to grow up like that, but at some point it became part of my ingrained behaviour and it's hard to fix once you get past a certain point. So do them a favour and kick the habit of pandering before it gets ingrained. (Some children do, I'm sure, grow out of it, but I won't be taking the chance with S&R).
Other ideas - do you get them to help with shopping/prepping/cooking? Might be worth a try. How about giving them each a pound at the supermarket and saying they can buy what they like with it, so long as it's a new thing (and not sweets, of course). Talk about what it might be nice to do with it, eg grated cheese on top or dipped in a boiled egg or whatever seems sensible...get their buy in and perhaps they'll be willing to give it a try.
I don't know if any of that is helpful. Some of the refusal might just be the whole asserting themselves thing. I really sympathise because it drives me batty when they don't eat what I've cooked, however easy or otherwise it was to cook.
Anyway, my thoughts for what they are worth.
I went out last night with friends, had a babysitter and all seemed fine. Got them up this morning (head pounding) and found poor S had a dirty nappy which contents had dried on his skin to the extent that going in the bath was the only way of cleaning him, and I actually gasped when I saw his poor willy. It looked as if the end had turned inside out, it was so red and raw and swollen. 'Just' nappy rash, but my god he was beside himself. He must have done the poo very early in the evening and had to lie in it, poor darling. He was very brave at the docs and we have cream now, but talk about feeling bad for not being there to spot it!!
I'm also just ludicrously busy at work again now, struggling to manage it all at the best of times, and this week with a cold and needing time off to deal with S this morning I am feeling rather stressed. Argh.