Habanero help

I am current growing jalapeños, tobasco, sereno, sugar rush stripey, and habanero. Everything is doing great besides the habanero. This is my first time growing in a raised bed as opposed to just planting in the getting.

About 3 weeks ago, the lowest leaves started turning yellow and they fell off while still soft. This continued and it's now halfway up my plant.

From researching online, i THINK that this is from a nitrogen deficiency. Any other thoughts? In az and it's already really warm. I don't water until top 2-3 inches of soil is completely dry.

Here is my question, if you agree about the nitrogen, can you recommend a good nitrogen fertilizer i can get on Amazon? Hoping for slow release granules.

Thanks in advance.