Glad to hear the ewe is improving in herself, that will help the milk supply.
When topping up a sibling group, I tend to think in terms of how much milk I need to put in to leave the mother a manageable amount of work, rather than worrying about do I give all lambs an equal top-up. So for instance, if it's triplets I'd like them to be getting 3L a day between them, a healthy ewe with a healthy udder on good grass should have no trouble producing 2L, so I'd like to get a litre into the lambs between them. Quite often, one of the triplets doesn't take to the bottle, so the other two get the bottles between them, and the third only drinks from mum. Frequently it ends up with one lamb apparently getting most of its feed from the bottle, and the middle lamb drinking a bit now and again, but not always taking any.
Your ewe may well be able to produce enough for two in her one good quarter once she's fully fit again, and if she's over the infection now you can probably assume she's producing at least enough for one already. So I'd be looking to see if the lambs will take a litre a day between them, and only worry if it's less if either lamb starts to look actually skinny.
Never over-fill a lamb, they don't know when to stop and it's incredibly dangerous to have the milk overflow into the rumen, but apart from that, I'd feed Fatty what he'll take and just give some to Skinny if you can. Personally I would keep having a go at catching Skinny and feeding him for the moment, they sometimes get keener on the bottle later on as they need more.
As Fatty is coming to you now, I'd feed him first; you might find that the sibling bond, curiosity and lack of pressure will bring Skinny closer and give you an opportunity to catch them both in the pen while you feed Fatty.
(To not overfill a lamb, I look down on the lamb as it stands feeding, and watch the flanks behind the ribs. As soon as it starts to be convex there, I stop. I'd rather underfeed at a feed than give too much, there'll be another feed later, and they'll get some from Mum in between times too. If necessary to give enough overall, I'd increase the number of feeds rather than risk overfilling.)