Hi, we have a small orange tree about 16" (inches) high above the soil
level in a pot 8" high and 8" in diameter. it's about three years old.

it stands just inside some french widows in a south facing location.
recently many leaves have gone brown and dry at the tips for about 0.25
inches long on the leaf and then there is a part of the leaf next to that
has turned yellow. the yellow part is also about 0.25 inches in length.

the pot is of the self-watering kind. that is it has a reservoir of water
below a grill. above the grill is the soil. so the plant is watered by the
water evaporating on to the soil above.

i have put some soluable photogen feed into the water recently, but only
after the leaves started drying and turning yellow.

does this sound simply like a short of feed problem please? or might it be
something else.