Pipefish are notoriously difficult to keep, many will only accept live food like, animated, and moving daphnia, copepods, mosquito larvae, and brine shrimp, dropped right in front of their nose,s and must eat small meals constantly throughout the entire day.
There are about 3 freshwater species here in Panama, and one that needs brackish water, some live in Lake Bayano with fairly hard, highly alkaline water.
I would only attempt to keep them if i could devote a tank only to them, with no other fish, and was breeding a ton of the live foods listed above. Much in the same manner seahorse keepers do.
I would also suspect the cichlid "might" have attacked them, but Tlindsey's theory of them starving (and been starving for a while) is most plausible.