oh my god, could this be the mythical titanium allergy? probably not, option one is that your tunnels might be high grade material, but their workmanship may be low grade, try taking them to a shop for cleaning, anodization (or maybe a high polish finish?), sterilisation and re-insertion

option two is that what you were told is titanium isn't actually titanium, most people get by just fine on good quality surgical steel, but don't do very well with low grade materials like aluminium and brass, and both of those are pretty light so they might actually pass for titanium if whoever is buying is unaccustomed to these materials and does't ask for the ASTM certification; you might wanna take into account how mush you trust whoever sold you them, this industry is anything but short on liars, thieves and cheats

option three is that years of using low grade materials has created a sediment of them within your earlobe's fistula, which is unlikely (meaning: stick with options one and two), and when you put in the titanium plugs you damaged the fistula and released these materials into your bloodstream, which is most likely not dangerous, it just might take some time for them to spread out, heavy metal poisoning takes a lot of metal to get going, much more than could ever accumulate in an itsy bitsy fistula

option four is that something is wrong with your ears, i have no idea what could it be, but it's still more likely than...

option five, congratulations, you have an allergy so rare that the medical community barely recognises it, and even where it does it's still seen as normally so mild that it's asymptomatic in non-immunocompromised patients, pat yourself in the back, you earned it