Had it happen once each on the L1011 and the A330. Both times had a lot of reverse on. My sense of it is, spoilers will affect the tendency for the nose to pitch up but will not, in themselves, cause it to do so under normal operational circumstances.
First thing I would do is call your flight data analysis team, preferably an association gatekeeper and ask to look at your flight because you're concerned about technique. Properly read data and some aeronautical knowledge should be able to help determine what the cause was.
I know you say "after deflare", but still ask, was the nosewheel completely on the ground when reverse was selected? Was the aircraft light, (around 160T or less)? Was the CG slightly more aft than normal? When did the nosewheel begin to lift, (what N1/EPR/Airspeed)? Was there a quartering tailwind - I've seen this as a factor in some tailstrikes esp if the speed is on or slightly below Vapp just before touchdown.
Your data analysis program will be able to tell you all this. If you don't have a data analysis program on the airplane, ask your airline why not. Then, try to recall all the above to learn why it's happening - it's not common for the airplane. Full reverse down to a full stop is permitted in the AOM if required in an emergency but one still must guard against pitch up.
The AOM doesn't specifically state that slight nose-down stick is to be held but a very slight amount won't be hard on the nosewheel structure and may prevent the tendency - ask your checking/training staff first though...this is an anonymous forum!
PJ2