I bought some trill a few years back now to test how fresh it was by sprouting it. I set it up exactly the same as my normal seed mixes and the only thing the trill grew was mould. The last time I looked into it it was full of tiny shells for grit, something budgies don't need.
I wouldn't ever advise feeding trill. Your local pet shop will have better mixes that they sell by weight. Always test sprout new seed mixes to see how fresh they are.
As for the illness has the little one been to avian vet? Has any bloodworm been done to rule out underlying issues? How long have they been ill?