I get a physio out regularly but I also do carrot stretches before and after every time I ride.
Watch Art2Ride on YouTube. It helps with not only sore or tense muscles and getting the horse over it's back but even kissing spine!
My horse responded well to acupuncture, mayo facial release and laser. Also Methacarbonal worked well to relax the back. Carrot stretches done correctly can help.
Lunging with the passoa is brilliant for getting them to streak their rump, back and neck x
Get some out to see the horse first but you could try putting poles on the ground make the poles odd so the horse has to look down make the horse stretch only do this at a walk you could also use white liniment
Hand walking over poles and turning the head/neck are good stretches and ecercises to try :)
Get a chiropractor out and they will give you the right stretches to do 🐴😊
Probably get chiropractor out and they'll give u stretches to do ☺