I think I may have cracked the Camphor puzzle. 
I think the key is Menthol which is also a Terpene derivative, just like Camphor. Menthol prices have shot up due to pharma sector procurements. Both share similar intermediates, as well as raw materials. (For example, α-pinene, which is readily obtainable from natural sources, is converted to citronellal and camphor. Citronellal is also converted to rose oxide and menthol.)
Here is some data I gathered for Menthol.
Menthol imports to India have come down by value and volume presumably due to shortages abroad, most probably China. This wouldn’t have directly affected Camphor industry in any way unless we were filling that gap by exporting Menthol. This is exactly what has happened. The reduction in imports also would have been compensated by domestic Menthol production, all of which would have stressed Terpene based products. Camphor is the predominant Terpene derivative in use in India. I suspect the increase could have also taken out the unorganised market which would have found procurements at higher prices difficult. If the situation continues, as it seems to be doing, going by last two months increase in realisations in Menthol prices, Camphor players will continue to have a good run. Tracking Menthol data might act as a proxy to play this theme.