I'll take a stab, my drum will cook faster so i adjust and not stick to a 3-2-1 or 2-2-1 i go by it being done (bend test or tooth pick comes out clean)
Do you use a deflector in your drum? I have done ribs not using mine and found it got done faster.
Long story short i think you over cooked them if they looked done and the passed the donenes test they are done regardless of time.
It all started with a Redhead! 22" Redhead OTS
22" Blue OTS
3 wheeler, Ethel (62-63)
3 wheeler18" Black OTS X2
18" Black Jumbo Joe,Mini-WSM,Smokey Joe
22" Blue Platinum OTP,
22" Black OTG (on sale for $99)
British Racing Green Thermapen
More grilling stuff than what i know what to do with