When I play every day my tone starts getting airy and I can’t play soft.
You have described what happens when one plays a spread embouchure. Playing TOO loud, TOO high (for your muscle development), TOO long and using MPC pressure.
If you keep going it WILL get worse.
Take 2-3 days off. Don’t let a mouthpiece touch your lips. Lip buzz for those 3 days. (This will help you to overcome the spread chop setting.)
When you start playing again play everything soft. Practice to see how soft you can play. (Again this helps to prevent a spread setting and works on range).
A very soft middle C has the same aperture size as a loud High C. Therefore you can practice making smaller apertures without the damage associated with range work.
Work on Clarke Technical Study #1. Stay below Middle C. Just use the Low F# to Middle c part of the exercise.
Work on good breath control.
LOOK where you are playing. A Low note needs little or no air support. Let them roll out of the bell of the horn. A Middle C needs to travel 10 – 15 feet in the air. A High C needs to travel 30 feet in the air. Higher notes require more air SUPPORT and they travel farther because of that. If you concentrate on how far you want to project the notes you WILL adjust how you support them.
After a week or 2 of this you should SEE and HEAR results.