You can use Epsom salts as it is a natural form of magnesium sulfate, add 1-2 tsp per gallon every 4-5 weeks is what mine says on the box. My Green Love Potion and Lambo plants looked a bit like yours do and I did this treatment and the progression has stopped and they are looking good. In fact, I witnessed a considerable increase in resin production in the days immediately following application of Epsom salt. This is probably due to magnesium's role in uptake and migrating phosphorus.