Your bees will. If there is not enough nectar to produce wax and they need it somewhere else, they will take it from your wax foundation. They may have taken it before they built out the rest of the comb.
If you want to put some out, I don't think it would hurt, but I think the bees might just as easily regard it as something to be removed and discarded as use it. They don't act upon our good intentions and many times find unexpected ways to thwart them.
When I think they need to be producing wax I feed sugar water....isn't this what they need in order to produce wax on their own? My experience with them taking wax from foundation is that it doesn't do well. Ecspecially if they are finishing off or making queen cells.