For a week or so, my puppy (Brittany, male, 5 months old) doesn't start eating right after being given his bowl, as he happily did so far.
The routine is like this: I take the bowl from his crate, call him if needed, then he follows me to the room where I keep the food, waits behind the baby gate and sits (we practiced that and as before he seems quite happy to do it, expecting the food). Then I put the kibble in his bowl, go back to the main room (he still follows me). When we brought him home (8 weeks old) he would then rush immediately to the bowl. He trained him to wait until I give him an "OK go" cue. Two weeks ago that was working perfectly, he was waiting, he was putting the bowl on the floor, waited a bit then released him and he would rush to the food.
Nothing else changed, but now I would not rush at all. He would just wait, unsure, and might even lye down.
After some time he would approach the food and start eating, possibly stopping half way, and finish the bowl later (say 5 minutes).
Sometimes as he waits one of the dog would approach and check the bowl, that usually makes him decide that it is time to start eating.
I don't know if there are reasons to be concerned, but I'm unsure about it.
I don't think it is the food because I reward him with treats all the time, sometimes he uses his regular kibble and he's happily taking it (one by one).
Could it be that it is only because he is teething ? I can see that his gums are inflamed.