Hi mummy, how long does the teat last before tearing?
I am using NUK's latex teats (also very soft) and I just had one that cracked too - my paediatrician did warn that these softer bottle teats don't last as long as the regular ones though he recommends them as good for newborn's latch. It only lasted 2.5 weeks for my 6-week-old newborn, so if the time frame is closer to this, then it's probably just that the teat damage fast due to the material and softness.
A second possibility is that I recently learnt we are supposed to replace the bottle teats every 2 months - so if the time frame is closer to this, then it might mean that the teat has just reached the end of its normal intended lifespan :)