Having major confusion with fitness levels!?

It seems that my Full backs, midfielders and from time to time wingers are always at the mark of around 50-60% by the half time mark and then they are hitting around 45% at the full time mark. Is this just me this is happening with? Any suggestions?

That's chronic, quite frankly!!

Anything less than 80% at half-time would worry me.

Have you created any custom training schedules?

If they started at 95+% the only thing I can think of that could make their fitness drop that much would be knocks. There are four types of injuries in FM: Carried off-injuries (black cross), can continue-injuries (white cross), knock from which the player does not recover, and finally knock from which the player recovers.

Strong heat and very wet conditions sap more strength out of the players.

What team/division are you? What are your fitness coaches like and what training schedules are your players on?

Those percentages are really bad.

Are you using fast tempo with high closing down?

(And carrying backpacks full of rocks?!)

Another explanation could be that they are not training...

Check if you have coaches in all the training categories and that your players are selected for a training schedule.

Other than what has been suggested so far, I really need more information to be helpful. Are you for example managing a semi-professional or amateur side?

Are you using fast tempo with high closing down?

(And carrying backpacks full of rocks?!)

Bingo.

Your asking them to do too much work on the pitch if you see this constantly.