Slack Tendons in rising 2yr old filly

[r0450111]

Both front fetlocks have dropped gradually. Its been coming on since 6 months of age. Farrier said it would correct itself then admitted problem was worse at 1yr. I'm looking for strengthing exercises/treatments (non invasive!) to help her out. When she canters and is tired, her fetlocks are almost on the floor. Filly has had light weights tied on to front fetlocks and road walked. Some improvement has happened.

Filly is not lunged or 'worked' other than handling. No she isnt insured either.

Thanks everyone for your help!