Iron supplements

Has anyone elses babies reacted to their iron supplement? Mine are 6 weeks now and I started giving it to them as instructed 2 weeks ago. The subsequent week they went from being pretty cruisey kids to miserable babies up all night with sore tummies. I forgot to give it to them for two days and they were again relaxed and calm and I even got to sleep!!! I'm not sure if it was a coincidence or not but I am too scared to keep giving it to them. Has anyone else had a similar experience? I know they need the iron, I was wondering if there's any way I can introduce it more gradually or if there's any way to ease their discomfort.

 

My DS would get constipated from the iron supplement. he was fussy when he was constipated. i had to counter that with pear juice which i hated doing.
it does not sound like what is going on with your LOs but just thought I'd put it out there.