Leaves Yellowing, Normal or from mites??

I'm getting yellow leaves at the bottom of the SSH plant that I've been growing. I just got a small spider mite problem under control, I tired a no pest strip but didn't do too much, so I used chili spray. Got rid of 'em after the second application. Now some of the leaves near the bottom are turning yellow. Are these just old growth leaves slowly dying off or is it a result of the mite problem? I've had the plant for about 2 and half months now, and feed them 3/4 strength grow nutes and feed full strength fish emulsion once a month. Any thoughts would be appreciated.

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