Not all babys sleep better on solids some sleep worse lol
maybe u should try bringing down the amount he has through the day back to one it could be causing him belly ache which would stuff up his routine
also does he have a fever rash seem really irratible through the day dribbling if so id be taking him to the doctors to make sure he is ok it might not be the solids could be sick or something
try giving him baby panadol before he goes to bed say about 15 minutes before hand
or even a bath before he goes to bed I find baths work wonders
my son is almost 7 months old he slept right through then got sick n didnt but he is sleeping again now