Start small
Changes in appetite, energy, movement, toileting, or behaviour can be useful to record for a vet.
There is no need to rush. A predictable, manageable step is usually more useful than trying to solve the whole situation in one day.
Try this next
Write down when the change started and what you observed, then contact a veterinary professional when you are concerned.
Notice what helps your dog stay comfortable and engaged, then repeat that version before making the situation harder.
Keep it kind and practical
Keep notes simple and current. For illness, injury, medication questions, or sudden changes in your dog, contact a veterinarian rather than relying on a general guide.