I should start by saying that I'm at the very novice end of novices.
I purchased a lemon tree that was on sale at our garden centre and it has done reasonably well for a while. After some time it did start to lose some leaves, but appeared to have recovered.
Fairly recently some of the leaves have turned yellow and I'm not really sure what I'm doing wrong - I have read that this can be due to magnesium deficiency, too much watering or too little watering.
I wonder if anyone can help - I've attached a couple of pictures to show what I mean:
(it wouldn't let me upload any images, so I'm hoping this link works)
Thank you kindly in advance