I've recently developed red stretch marks - will this Tretinoin 0.05% w/w gel help improve them?

Tretinoin is sometimes used off-label for early, still-red stretch marks, and it can help fade them a bit faster since it encourages collagen turnover - but it works better on fresh marks like yours than on older, white ones. Results are gradual and vary quite a bit from person to person. A dermatologist can confirm this is the right strength for the area and guide you on how long to continue.