My youngest had a cold basically her whole first year!! Nothing more than a runny nose really, but there was always something.
At 9/10 months, she was barely drinking 2 bottles (a bedtime one and A night feed) as she just was not interested in milk at all, and at 14 months she stopped drinking milk at all, and still wont to this day.
She had cut all 16 teeth by 14 months, and I did go through alot of 'phases' where I would give calpol before bed, in the sheer hope that it would help her to sleep... Not that it ever really worked, but I was desperate and knew she was teething.
Her diet isn't the best either. She has had crisps like skips/quavers etc from when she started food at 6 months. She has two sisters who are still young so alot of food gets shared (or stolen!) and it was kind of unavoidable. Fish fingers etc I dont even think they are that bad, and tinned/packet stuff might not be the healthiest/contain the most goodness, but I doubt they will be doing any harm.
In all honest, my now 17 month old eats pretty horribly, was on 3 meals and snacks with no daytime milk by about 8/9 months, is smaller than alot of babies her age, had her fair share of calpol as well as a never ending cold... And I blame shit luck 😂
Your friend is probably struggling, and doing whatever she can to get by. We dont all get 'textbook babies' and its not always possible to do everything perfectly.
Hopefully as the nicer weather comes in, her little guy can catch a break and build his little immune system back up. And in a few months he will be totally different, and your friend will be very happy that you have been there and supported her when she needed it xx