Potatoes don't like it hot. That may have been your problem. That plastic tub may have acted as a heat sink and overheated the soil. Do you have a place to grow them in the ground? Next go-round, I suggest that you grow them in the soil, and give them a good heavy mulch. I plant my seed potato in a trench, pull the soil over the pieces. Then, I wait till they sprout. As they sprout, I heap the mulch on. I use old hay, grass clippings. That mulch wants to be at least 6 to 8" thick by the time the plants bloom. Of course, I'm only familiar with growing potatoes in zone 4! Zone 9 is a whole other world! They can be planted here: 3 weeks before last expected frost. I suggest that you contact your county Agricultural cooperative exchange office. Usually associated with a State college system that has an agricultural program. You can do so on line by doing a google search. They will most likely have articles pertaining to growing potatoes (and any other crops!) in your planting zone. They will also have lots of articles regarding food preservation and animal husbandry. You can read them at your leisure on your computer! You can also get your soil tested (for a nominal fee) through them. Our tax dollars pay for this service, but few folks are aware of the many services they offer.
Ask: what breeds excel in your zone, and when the optimum planting time is. There are also early, mid and late season spuds. I suggest you choose an early season spud, and plant it to take advantage of your cool growing season. They like it cool, yet the foliage absolutely can't tolerate a frost.