Health problems are just around the corner for you, buddy.
You can always claim that with anything some health problem is just around the corner. "Oh you quit smoking five years ago. Just buckle up, year six is when the cigarette nutrient withdrawal really is going to kick in and you'll be back smoking in no time". This is not really an argument that demonstrates anything significant.
Yours truly has been told that health problems were "just around the corner" by keyboard warriors since becoming vegan. This doesn't discourage anyone from the next goalpost move. "Oh it's month two that you'll start to feel bad" "Oh it's year two". I'm sure that 97-year-old vegans hear that "98 years old is when the veganism really catches up to you".
Any person can also then make the same claim about any stance. "Oh you aren't a Muslim? Just wait, Allah will reveal himself to you soon. Something will happen soon. I just know it", or "Oh you don't believe in passing horrible law X? Just wait. Our country is going to collectively pay the price soon!" You can defend any position with this: political, personal, or ethical. This doesn't actually prove anything.
If you want to claim that veganism is harmful, you would need some epidemiological data demonstrating the truth of this claim. This is true for any "you'll see soon" claim.