Possible causes of deal larvae at entrance without signs of chalkbrood:
1. Natural reduction of drone brood due to time of  year.
2. Trimming of brood due to lack of nectar flow (which applies to 1 also).
3. Pesticide exposure. Are you in a corn area? I am from Michigan (now in
Connecticut), and since corn is in tassle in this region, dead larvae are
often a sign of pesticide exposure. Is colony population reduced?
4. Manipulation mortality. Were you just into the hive? It could be that
these are larvae killed during manipulations.
Larry Connor