the growth to how i got a mimitchi just today ^^
Shirotsubutchi > Petitchi > Ringotchi > Mimitchi!
observations : intelligence was about 40, arts about 6 and social about 3 when my ringotchi changed into mimitchi. weight was pretty low and games were played pretty often. my tama was a girl and on gen.3 with a fair amount of pausing. hearts dropped to two at most but were mostly kept to at least three hearts or full. no treats (food bought from store) were given, no items used.