Grapevine blossoms

I have Catawba (3-4yr old), Canadice (3yr old) not receiving full sun.

Neptune (2yr old, still in leafing out), Tickled Pink (3yr old) both receiving good sunshine. I am worried that I won’t get any grapes from them cos last yr I had 2 clusters from Canadice but they shriveled and came to nothing.

Any suggestion to make sure that I do get a few bunches of grapes from them? thanks in advance.