This could be due to higher impediment in candy components networking determined by the presence of physical particles of higher dimensions. A different behaviour was evidenced by Habilla, Sim, Nor Aziah, and Cheng (2011), that studied the properties of candy made of acid-thinned starch supplemented with konjac glucomannan or Psyllium husk powder.
The authors found that the hardness of fresh candies decreased with the addition of Psyllium but the phenomenon inversed during a storage period of 8weeks at 30 C; the authors motivated their observations with a delaying effect of short-term starch retrogradation.
Nevertheless, it has to be understood that starch gelification and retrogradation, as well as Psyllium gelling properties, are completely different phenomena in comparison to those related to pectin networking and fibre organization.