Its a real roller-coaster owning these bleedin sheep in't it!?
I would tell you not to worry - but worry we all do and its the worry that makes us keep on the ball and looking after the rest of em. The death of an animal is very hard to deal with - I dont think it ever gets any easier, I always shed a spark of a tear whenever something dies in my arms or I find it stiff in a field, legs out. You always blame yourself, well I do.
One of the problems with caring for animals is that there is so much conflicting advice, even from professionals, but thats the same in any industry you look at.
My guess is that most people find out whats 'right' for theirs through experience, experience also gives you a better standpoint to judge other peoples opinions and experience.
You sound like your doing a fab job looking after them, sorry to hear you lost one too and I hope they all get better and have a good old life munching the goodies you give them.
Baz