Maybe simply a humidity level issue ??
I did this very successfully with my SD Retic who's viv was heated with a 250W ceramic that was very drying ..
The trick with many (and certainly Royals ) is to wait until they go blue / into shed ( they usually disappear for a few days ) then ensure you spray the viv well daily ...
THEN crucially when they make an appearance and get their colour back / eyes clear ... you should spray well each morning and evening ( and between if poss) they will normally shed perfectly each time ..
You will usually find their shedded skin in a filthy rolled up mess under a hide somewhere a few days later
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