Sounds like they're going well with it
At this age, milk is absolutely essential and shouldn't be displaced by too much solids, generally speaking.
While my son ate from 6 months and would be having 1-2 small meals at that age, my daughter still could not have food in her mouth without gaggin/vomitting till over 7.5 months and din't really eat anything till 8 months. Neither slept well, both were growing and hitting their milestones (which are far more reasonable indicators of how they're going. Sleep, sadly, is irrelevant).