Oh, Fiona and the gang seriously fucked up, didn't they? In the previous timeline(s), Albus started his quest after the hero Rayman had succeeded in his quest of curing the Red Blight. Or rather, Rayman's quest allowed Risa to finish the cure after he'd "died". Except he didn't die. He just Revolved himself out of reality. Albus' starting timeline was Rayman's last Revolve; he'd finished his heroic duty and things were OK. Only Risa remembered him because no one else even knew there'd been a hero's quest.
Then Gina used turbo-Revolve and accidentally Revolved all the way back to Rayman's quest because no one in Albus' party knew about Rayman. In doing so, they undid Rayman's last try and reset the situation to back before he'd started his quest. Only, this time there's no more Rayman the hero because he's already out of the picture from Revolve overuse last loop. In fact, he got erased out of reality altogether. That's why the Red Blight got so bad this time around. No one was able to create the cure since Rayman is no longer able to pass on his knowledge to Risa.
One big hole in this theory is the assumption that Rayman was also a hero in Albus' og loops. Unfortunately, it has been heavily implied by Albus himself at the start of this arc that there was no Rayman the hero in Albus' loops.
In chapter 49, Albus stated that he was supposed to have been chosen as the hero when he was 5 and in the middle of his hero training by the time Merida contracted the disease, when he was 9 (which is his current age). That was not the case here as Albus hasn't been undergoing any kind of training. It's safer to assume that he is currently in a whole new timeline altogether; Rayman the hero's loops.
Their loops never exists in the same timeline.
Albus (5) was chosen as the hero > Hero training > Merida passed away (Albus: 10 y.o )> Loop start
Rayman was chosen as the hero > Loop start > In the latest iteration, Albus (9), supposedly a normal kid, joins Rayman
The reason the disease is acting differently is more likely related to the fact that the Demon King also remembered about Albus' loops, not about the existence of the cure.