Children & years past in the final episode/S2 ep 13

I recently saw the final episode of S2, ep 13, and I'd been just curious to know how many years were supposed to have passed before that episode, especially considering how much or little they aged the children?

In this final episode, we see Elizabeth's children Geoffery Charles Poldark return from boarding school suddenly aged to about 16 or 17 years old, even though for most of S2 he'd been played by the same young actor from S1, and appeared to have been about 10yrs old through most of it. Along with teenage Geoffery Charles, young Valentine Warleggan (who'd been born in ep 1 of S2) is also shown riding a rocking horse & interacting with his parents, and he seemed to be suddenly aged to between 8-9 yrs old (based on how old the young actor playing him looked in real life at the time.)

In the same episode, Ross & Demelza Poldark's two children Jeremy & Clowance are finally briefly shown in the final episode of S2, however they were aged to only about 4 or 5 yrs old for Jeremy & 3yrs old for Clowance...even though Jeremy was born in S1, long before Valentine, and Demelza was pregnant with Clowance seemingly not long after Elizabeth had given birth to Valentine in S2.

So as an odd inconsistency for the series, either Valentine Warleggan was aged far too much in the series finale (or too old of a child actor was cast in the role), or Jeremy & Clowance Poldark weren't aged enough for the time jump? lol (I wonder which way it was supposed to be?)