There is no evidence to suggest any change in GA application rate for older tubers in successive cropping cycles ( T2,T3 etc)
Key points to watch
1. Ensure any diseased or calcified ( chalky) tubers are removed
2. Pregerminate (uniform temp 24°C and humidity 90% for 7-10 days) so sprouts are beginning to emerge
3. Spray to runoff with 100ppm GA plus fungicide/insecticide mix
4. Allow to dry
5. Plant within 1-2 weeks as GA effect can wear off over time.