Q.why are my tomatillos falling before the husk splits
Pineapple tomatillos are dropping before husk splits. Some are turning yellow and some are still green. There are loads on plant. They are in greenhouse.
This could be temperature related due to being in the warm greenhouse.
They can ripen some off the plant so I would certainly use all the fruit.
Also even if the husk doesn't split they can be ripe. Look for the the papery appearance as a guideline.
https://www.gardeningknowhow.com/edible/vegetables/tomatillo/harvesting-tomatillo-fruits.htm
https://www.gardeningknowhow.com/edible/vegetables/tomatillo/growing-tomatillo-plants.htm