sore arms

To any and all,

I have 4 pitchers with sore arms despite my best efforts to prevent it.
We stretch for 12-15 min. before every practice then we add 3 sets of poles as a warmup before we start throwing 1st at 40ft and gradually working up to long toss at 90' .These are 13/14 yr olds playing on a 80' diamond.Bullpen session have been limited to 30-40 pitches once a week in addition to 3-4 games a week.No
pitcher has thrown more than 50 pitches in a game and no more than twice in a week.I have them ice after every bullpen and everygame they pitch in.What more can I do.
Pitcher #1 has a tendency to twist his arm when he throws so I have him working with a stripped ball to show him his rotation on the ball so he can see when he is twisting.He along with one other pitcher who does the same thing have been doing it for a long time and it is a habit I do not know if they will ever break.I suspect this is the cause of there sore elbow.My #3
pitcher is 5' 4 and 98lbs soaking wet and has had arm problems for 2 years I have studied his mechanics and can find no flaw that would cause this.He doesn't throw across his body he finishes with his throwing arm outside the opposite hip and he uses hie legs well ........

Can anyone suggest any possible solutions I am getting desparate.I do not want to ruin a kids arm and by shutting down some of these kids I am rapidly running out of pitching.

Seadog

P.S.I am going to check the archives next.