Sorry to read about your losses. Hives that seem robust in late January can crash in March for various reasons, the queen might have died and they aren’t able to produce another, then the cluster will dwindle eventually reaching a tipping point and will not be able to generate enough heat to stay warm enough.
If there is no apparent dieses and you think you hive is in trouble of running low on food reserves I have had good luck on sorting out frames of honey and pollen and adding the super on top of the hive in need. They will just move up and take advantage of the new food.
I will also use frames of comb and honey from dead outs to start packages on, they will get a good head start in development because as soon as the queen is released she will have nice cleaned cells to get busy in.
If you are not going to use the frames form the dead hives right away protect them form wax moths or they will surly find them and destroy them. I have had great luck using B-401 you spray you stored comb and moth problems solved. You can get the powder form from Sundance on this forum, for a very good price.
Hang in there bad years happen for a lot of different reasons.
The Busy Bee teaches two lessons: One is not to be idle and the other is not to get stung.