I agree with growth spurt. Just give them more milk for a bit.
It can still be early for solids. If they are not ready then give it a miss for a week or two. My DD is over 5 months now. I gave her a little food but have stopped the last few days as she is not quite ready. As of yesterday she has started to really look at me/DS eating and has been grabbing at the food. I will try again in a few days as she may be more ready.