Player Development

I have a problem with player development. It's taking a really long time, too long.

For example I bought João Neves at the start in August when he was at 79. After 2 seasons he was at 85. This is where it gets interesting. I sold him to Tottenham at the end of the second season. In the same transfer window, I checked the market. After not even a month, he was 89!

The same thing with Sesko, he was stuck at 84 after 2 and half seasons. After I sold him, he was 88 in the same transfer window!

My strategy is to get players up to 5 star weak foot, 5 star skills, a plus plus role, then put them on balance.

Am I missing something?