I started the same way last year...two nucs that limped along after one went queenless and I used the second to feed frames of brood. I continued for about 5 weeks and then bought a queen to install. Both strengthened enough to make it through winter. I chalked it up to part of the bee initiation program. I learned to exchange frames, install a queen, etc. Those same "weak" hives exploded and taught me this year's lessons on attempting splits, swarming, and re-combining hives. I wonder what they will teach me next?