Start with Oxiclean. Wait for fxh rant if that does not work.
Matthew 18:20 :: 20 For where two or three are gathered together in my name, there am I in the midst of them.
Collar and cuffs will mainly be bodily fluids (sweat). These can "set" in.
Dry cleaning can often set them almost permanently.
Washing is best.
Soaking is what gets rid of most stains. Length of time soaking is important. Longer is better.
Just soaking in water will generally be OK. But soaking in Napisan (or equivalent) is better.
To simplify the Oxy/Napisan makes the water more watery and penetrates better. (Aldi is as good as the others - possibly made by same people anyway)
A 24 hour soak is good.
A lid full (perhaps 2 x table spoons or less?) of Oxy in a bucket, mix it up, and throw in a bunch of shirts.
It brings white shirts up very well.
I do most shirts every few months.
Don't leave shirts in laundry basket with stains on them - they will tend to set - ideally you'd have a bucket of water and as you took shirt off you'd throw it in water to soak straight away until wash day.
Please notify reception on your way out that this consultation will be Bulk Billed