problems with training

[mrevildogood]

i want to train my players naturally but for some reason i cant improve the defensive attributes of a player (a defender) when a skill point is achieved, it allows me to improve, physic+mental, attack and special ability. why cant i improve his defensive attributes and how can i fix this? (i know it isnt maximum because i have other players with higher defensive attributes)
thanks

[Kukilon]

You have reached the maximum difference of ex amounts of skill points between the highest and the lowest. If your raise your lowest "attack for you I guess" you will be able to spend more points in defense.

[July Fourth]

You cannot have one area that is more than 20 higher than any other area.