Since my nephew started daycare all he does is grunt. Is there something wrong with him or the centre.?

He is almost 13 months and used to say 'dada' and 'ida' and babble, but since he started daycare all he does is grunt. The workers say he's also very clingy to them. Please note he was born 1 month premature. Is this a developmental problem, or a problem in the daycare. My daughter has been in the same centre since she was a year and she's talking up a storm! She's now 17 months.