Players dropping PA points

Hello, I'm Arsenal in my 2nd season (November) and this is the first time it happens to me. I Buy a player with good potential ( 3,5 *) that later (2-3 weeks) transforms into a ''decent potential'' player ( 2,5 * ) . It has happened 2 times already for me, namely with Sergi Gomez(from Barca B) and a young promising CM , James McCarthy. They were both rated 3,5 * when i bought them, and a while later they both become 2,5 * , rated BY THE SAME COACHES. They didn't drop any atribbute, they've been given playing time, they're not unhappy , so : What is the reason ? Could it be a bug?

Or perhaps you didn't scout them thoroughly enough before buying them? Now they've had a proper look at them they can give a better rating of them.

Scouts rate players compared to players in that position in your squad.

That means generally a players scout pot will drop as other players in your squad get better, or you buy better players or the players your scouted don't improve as much as they could have (due to lack of games, training etc.)

Did they have a birthday? Age in years is one of the factors coaches take into account when working out "PA".

The players aren't getting worse (PA can't drop, actually), it's just one of the weaknesses of the algorithms SI use.

Well i didn't buy any players after them, so it couldn't have been that , and there's no player that could have improved massively to bring the defence to the next level. And Sergi Gomez was scouted several times before being bought by my best scout, Francis Cagigao , he always got a 3,5 * , now all of my coaches ( they have high ca/pa judging) are giving him 2,5 stars. Their attributes improved a bit, not very much, and Sergi Gomez was tutored by Diego Milito.Their performances have been decent(6.8 ish), Gomez did make a few mistakes in the defence and ocasionally got a 6.6-6.7, could it be that his PA was reevaluated as a consequence of their performances?

Actually ,you're right SCIAG they've both had a birthday after arriving at arsenal, and i reckon that's when the rating dropped, so it looks like i've found the cause, thanks. So i guess scout reports aren't so reliable after all , especially just before they have their birthday. What do you suggest to do in order to find a player's true potential then ? Or is it just the result of their atribbutes not improving/no playing time at their teams ?

Scouts rate players compared to players in that position in your squad.

That means generally a players scout pot will drop as other players in your squad get better, or you buy better players or the players your scouted don't improve as much as they could have (due to lack of games, training etc.)

This. It's all relative.

Actually ,you're right SCIAG they've both had a birthday after arriving at arsenal, and i reckon that's when the rating dropped, so it looks like i've found the cause, thanks. So i guess scout reports aren't so reliable after all , especially just before they have their birthday. What do you suggest to do in order to find a player's true potential then ? Or is it just the result of their atribbutes not improving/no playing time at their teams ?

The best way to find a player's true potential is to wait and see

I would suggest that you go by the higher number of stars (that they had before their birthday), unless they really stagnate then there's no reason why they can't still get to that level.