Dont think its any problem to continue, but your tri 2 vitamins should already contain folic acid, so eating extra prolly won't help much except waste money, and also, it might give you more nausea than you already have.
Currently in 2nd trimester as well. My gynae told me to stop taking the folic acid supplements as the other pre natal vitamins will contain some folic acid too.
Yes it is recommended/advisable to stop at 12 weeks and thereafter continue with your other pre natal vitamins.