The best thing my mother ever did for me was to buy me a baby scale. My son was a preemie, and the hospital told me to wake him up to feed him every two hours, but he never wanted to wake up. She went and bought the scale and told me to weigh him, and that the second he began to lose weight, I could worry. He never did, and I never woke him up to eat again. Babies eat more when they have a growing spurt, less when they slow down, and less can seem like almost nothing sometimes. If he is not losing weight and seems to be getting better, cold-wise, he's probably fine. You don't say how old he is now, but since he's on baby food, he's probably big enough that not getting enough to eat won't hurt him in only a few days, so it's not an emergency situation, it's more of a wait and see one. If you notice him losing weight, by all means take him to the doctor right away. Same if he's not getting better from the cold or if he's way more fussy, lethargic, or spits up alot more than before. But if he's just eating less, it's probably fine.
My second daughter had projectile vomiting from birth until she was probably 8 or 10 months old, then threw up more easily than the other two all through childhood. I took extra cloths for both of us everywhere we went. But she kept growing and gaining weight, and I had several friends who were doctors who said she'd be fine as long as that was the case. A friend of ours had a baby with the same condition and he ended up having surgery because he was losing weight and getting dehydrated (he's now 19 and 6'5", so he did just fine.)
Rule of thumb--babies shouldn't lose weight generally, and if they're growing and gaining, they're likely to be fine.