i always introduced a new food first thing in the morning because this gave all day to see if there is a reaction, far better to deal with in the day than at night
at 5 months i think solids is really only to get them used to eating, trying to establish solid feed, getting them used to it for when it is really necessary, milk is far more important, so i would just top up with solids
i am no expert, this is just how i felt and dealt with it, hth
sylvia