shaolig

Hi,
I have a 3 yr old who has been diagnosed with CP and Cvi(cortical Visual Impairment).He has just started preschool.My concern is that lately he has started licking everything that he sees with his tongue-so basically if we give him a toy instead of reaching out with his hand he brings his head forward to lick it.So far he does not have any issues with eating and swallowing as he can have all textures and eats everything.This has been happening over the last 3 weeks and nothing seems to help.Does it indiacte some sort of deficiency (mineral/vitamin) or is it sensory?
Any inputs on what can be done to stop this behaviour is highly appreciated.
Thanks
Shaoli