[Scandia]

Yup, the Turtles were infants when they were mutated.

Yoshi had passed away a while ago. It is possible that Splinter may have just obtained his ashes somehow. Or that he felt that the Turtles were finally old enough to handle a trip to Japan.

It is possible that the Ancient One was telling this part of the story and that he somehow thought that Yoshi had died very recently- when the truth is that it had been a couple years. Just like Splinter mentioned knowing that Shredder was an Utrom (by the time he tells the story, he did), it is possible that the Ancient One mixed up the details as well.

I did have a hard time distinguishing the Turtles. It took me various times rewatching to tell them apart. The only one that was clearly discernable was Donatello.

And many foods do alter people's secretions and excretions- odor, texture, and color wise.