That will almost certainly happen if you try & clean any water based acrylics out of the brush with cellulose thinners, not just Citadels. For example Valejo, Lifecolor, Revell, Humbrol etc.. They should only be cleaned out with water, or for stubborn deposits something like Isopropyl alchohol or specific airbrush cleaners can be used, although if I use IPA I'll always finally flush the brush through with water.
The problem is in the terminology, as Tamiya and others such as Gunze Mr.Color (the non 'aqeous' type) are what are now termed 'laquer' based acrylics. These can be thinned/cleaned with cellulose, their own thinners or even some window cleaners/screenwash solutions (they're useful as they're cheap!).
You can easily tell the difference between the two, as the laquer based acrylics have a very much stronger smell than water based ones which have little or no smell.
One other thing to watch for if you use cellulose thinners through some airbrushes is to check what the internal seals are made from. Both my Iwata's are no longer in use as they have rubber seals which have disintegrated through repeated use of cellulose thinner. I've replaced them with a Harder and Steenbeck Ultra and an Evolution, both of which have PTFE solvent resistant seals
Keith