If you can get the money together and find a reasonably priced vet, it should be under $100 for an office visit and a round of antibiotics if their only problem is an upper respiratory infection. The yellowish color makes me suspect a secondary bacterial infection to a herpes virus or a feline chlamydia infection. They also need to be dewormed and a good flea preventative (FELINE advantage/frontline) applied.
good for you for taking these little ones in...I will give you a link to a post I did earlier with the same info. you need to give these kittens wet food and mix in the required amount of an amino acid called L-lysine, this is very effective UNLESS it becomes bacterial than they would also need an antibiotic...
let us know how it goes...:))
http://www.medhelp.org/posts/Cats/My-Kittens-Eye-Wont-Get-BetterNeed-Advice/show/1911041?personal_page_id=861539