Kaleb had a solid strike during the week and we had recently changed him from the Stage 1 to stage 2 formula. I put it down to his body adjusting to the new formula so your little one is probably doing the same.
I just kept offering solids (he started to suck it off the spoon which was outside his mouth

) and he's now pretty much back to normal although I am waiting a bit longer after a bottle before giving him his solids (he used to want them straight after finishing bottle but now doesn't finish whole 200mls then wants solids about 20-30mins later).
HTH