Tying up or Rhabdomyolysis is a painful and damaging condition for horses. This video is a simple tip of the iceberg look at why it is so very important to diagnose what is going on with your horse so that you can get the treatment and diet correct.
If you have a Warmblood who is just underperforming, it could be showing signs of MFM which is sometimes confused/mistaked with PSSM2.

Time stamps.
1:20 Rhabdomyolysis
2:40 Symptoms of Tying up
4:00 RER (recurrent exertion rhabdomyolysis)
6:20 PSSM1 and 2
6:50 Warmbloods and PSSM 2
8:20 Warmbloods and MFM