Thirty since you split so soon after you received your nucs in May I am assuming you are not after honey this season but more so after building up bee colonies? Is this correct? (It is to late to worry about gathering honey anyway.) If that is the case and is still your desire, then you are on the right track by feeding. But feed alone is not enough for a colony to prosper. (Raising new brood). They must have an endless supply of food and Pollen or pollen substitute.
How many frames of BEES do your nucs have? Two, Three, Four? Does each nuc have drawn out frames of comb? In your area or at least in my area it is not to late to keep the nucs headed into fall and winter. If you have the bees per nuc, comb, and good queens. However you will have to feed feed feed. Again comb is a must, not only for food storage but brood rearing. It is to late to expect much new comb to be drawn. You should already comb on hand and in the boxes. .
Many will tell you it can?t be done this late but I have done it. Thanks to the encouragement of Mr Live Oak here through PMs and David at Barnyard bees via phone, text, and comment section below his videos. Let me reiterate, pollen sub must be in steady supply. Open feed pollen sub close to your yard is what I advise. Keep it available constantly. I did the same my first year (late fall) with splits using MATED queens about this time of year and ALL my splits not only made it through winter but came out of winter packed with bees and thriving.
I left feed in front of them the entire winter, both sugar syrup and pollen sub, via open feeding sub and top feeding sugar syrup, your bees will thrive as long as they are healthy, have enough , and comb per nuc, bees, feed, and pollen. On the warmer sunny days 43f and above they will indeed fly gathering pollen sub. They will fly in abundance at 50 . Yes feed feed feed if you are seeking colonies.
Blessings
ie I used broadman style feeders and still made it. I advise the method of top feeding. with the same style quart or larger jars. This method, when feeding sugar syrup is much bette for winter feeding nucs for obvious reasons.
PS Bob I caught one and got tickled as I thought of you The phone changed reasons to treasons. I changed it back to reasons lol 😂.