Hello, and welcome.
It would be best if you could bring them inside, with the mother, if she will allow, to care for them and watch more carefully, to see if she is nursing and/or nursing enough.
For their eyes, take a warm, dampened cotton ball and gently clean the matted areas. It may take more than one go at it, to get it all off, but don't pull of any hard matter, just soften with the cotton ball, use one, then throw away, and use a new one for each eye on each cat, to avoid cross-contamination. If they are younger than 10-14 days, their eyes should not be open yet, but if they're about 10-14 days old, they should be able to open their eyes after you clean them. It sounds like they have an eye infection, so, for the moment, until you can get them to a vet, place a warmish, damp (wrung out) regular tea bag on their eyelids and this will help draw out infection.
If their mother is feeding them well enough, their bellies should be rounded and they should not be crying a lot. However, I do believe you should have them seen by a vet as soon as you can, because if they have a bad infection in their eyes, and it goes untreated, this could end up in blindness.
I hope all will be well with these tiny babies!
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