Dear J.,
I'm with Judy T on this one. I think you should start with stopping the solids and see if there is a change. Your lttle girl is only 5 months and can wait a bit longer for stage 1 foods.
My son too is 5 months (breastfed) and I started him on rice and oatmeal baby ceral at 4 months. Just a tablespoon a day mixed with breast milk and he was doing fine. When he turned 5 months I started to introduce him to stage 1 orange veggies and he had the opposite effect; loose mucusy stools. We stopped all solids and he's back to normal. He's just been tested yesterday for a milk alergy (blood in stools and fussy after I eat diary, since birth). I've been dairy free for 4 months now and I need to know if he has a milk alergy or just intolerant. Every time I try to reintroduce dairy into my diet the same thing happens with the fussiness and blood streaks.
Now with my daughter who is now almost 4 (was formula fed), and when introduced to solids she was constipated like your daughter. What our ped recommeded was to give her one jar of prunes a day; either by spoon or if desperate in her bottle mixed with formula. Also a couple of ounces a day of Gerber Pear Juice. We did this to keep her regular for MANY months. Every now and then I would stop the pear juice and prunes to see if she would get constipated. I did this until she wasn't anymore (close to her 1st birthday). With constipation always think P's; Prunes and Pears. And when she gets older, always keep fruits and fiber in her daily diet.
Good Luck!