they look a little droopy, which is usually caused by overwatering, which causes the roots to be in water and rot. how old is the plant? what nutes are you using? yellowing leaves at hte bottom usually indicates a nitrogen deficiency.
Don't worry too many people worry if the bottom leaves yellow the bottom leaves are the first to grow and normaly the first to go.this is normal often the odd leave will die same has every other liveing plant there is always the odd dead or dieing leaves.but 2 many people start adding fertilizer's when there not needed.if any start yellowing further up the plant then worry,but too many folk are 2 fast to add nutes the first sign of a yellowing leave.the pictures of your plant look ok it looks healthy.a little tip on watering let your plant dry the top 3 ince of soil before re watering.by doing this your plants will not become prematurely root bound.
I am having the same kind of problem. Would adding Mexican Bat Guano help for nitrogen? If so, how soon should it be added? Can the Bat Guano just be added to the soil at the start so maybe this wont happen?
fdd...LOL.. found a yellow leaf..... The humanity......
Don't go throwing N at a normal bottom leaf loss... just watch that it doesn't move up the plant..if it does then N may be the issue... like hair..old dies... new grows in its place at the top... Luck..