Did I over feed or under feed?

[CanadianCitrus]

Good day all,

Another challenging winter of trying to grow potted citrus indoors in the frigid zone 3A. I have a Navel orange in a 1 gal container and a Eureka lemon in a 4ish gal container. They are in side for the winter as there is snow on the ground and it is -15 degrees Celsius outside ( like 7 degrees F). I have noticed over the last few weeks that there are some light spots showing up on the leaves of my plants. I fertilize ever 2 weeks still with a 30-10-10 fertilizer with trace minerals. I continue to fertilize as they are still pumping out lots of new growth even under CFL bulbs that run 17 hours a day. For the majority of the day the temperature is 69 deg in my basement with a high of 71 and a low of 63. There are no signs of root rot as off the last time i re-potted. Im worried that I have either over or under fertilized. I fertilized the same amount in the summer with great success but the leaves on my lemon tree are not getting as big as they were when I bought it from the nursery.

Below are some pictures. Cheers!

[lebmung]

It can be salt build up in the potted soil. The plants don't use all the nutrients. This plus the carbonates from water soil will block nutrients uptake.
Try to melt snow and drench the pots untill all the residues come out.

[CanadianCitrus]

Thank you for your reply. The plants are indoor plants and are not exposed to snow. However, I have heard of salt build up I have tried to flush the plants as best as possible when watering.

[lebmung]

You need to flush the soil with rain/snow water, not chlorinated alkaline water from city network. Also water needs to be slightly warmer, like 35 C to dissolve the salts.

[Millet]

I don't see any symptoms of a salt build up in your container.    A salt build up shows a burring of the leaf's tip and along the leaf sides.  In Canadian Citrus's first picture I'm not sure what going on .  The second picture is showing several leaves with a manganese deficiency.  Some might think it is a magnesium deficiency because of the darker green delta shape, but it can't be because magnesium deficiencies show up on a tree's older leaves.  To correct a manganese deficiency you can apply manganese sulfate either as a foliar spray, or to the soil, OR you can simply do nothing.  New ctrus leaves very commonly show a manganese deficiency, almost always they grow out of it as the leave matures.  During the winter months water your tree with a lukewarm water (70 - 80-F) solution.  This will help the health of the root system, and fertilizers to reach your tree more efficiently.