All of the nap issues and fussiness started the day after starting solids.
I think if you feel it was the solids then it could well be. I've seen quite a few threads over the last couple of years with some sleep disturbance when solids are introduced. More often I've seen night sleep disturbed but it could be naps too. My DS certainly had bad sleep when we introduced solids but it resolved reasonably quickly. I made sure solids were 1.5hrs before sleep (it's hard to fit it all in the day to begin with!) with the hopes any gas would pass before sleep, this helped a lot. I also avoided fruit before sleep but that was because I have a silent refluxer and I felt fruit might be too acidic before laying down.
I also considered possible over stimulation with intro of foods because it is a totally new experience, smell, flavour, texture, eating something that isn't milk, being given a sippy cup, sitting in a new high chair. It's quite a lot to deal with really, like getting a new toy but one that stimulates all the senses in one hit.
It's not necessarily a food allergy or routine issue, although of course worth considering everything.
