Often something that comes on so quick like this can be caused by an active ulcer on the eye/lens. That can be caused by trauma, infection etc. You will want to have the vet do a stain I think, and check for ulcers before anything topical is prescribed for the eye. Steroids to reduce inflammation can infact cause the ulcer to erupt, destroying the eye. One of my bunnies was really young too when he developed cataracts and eye issues, younger than a year for sure. Its really hard to know what is happening to it but I hope this is something totally treatable though, keep us updated.