Orchids take up urea nitrogen just fine. Information to the contrary was debunked long ago.
Manganese and magnesium have no relation except both begin with the letter M.
Plants incorporate one magnesium atom in each molecule of chlorophyll. Lack of magnesium is a possible explanation for why your plant is so pale. Chlorophyll is damaged by sun exposure over time; lack of magnesium prevents plants from forming more. Magnesium deficient plants in too much light become paler and paler.
Plants need a little calcium, too, but not a lot. Plant roots actively exclude most calcium to prevent the plant taking up too much.
Are you diluting your fertilizer with tap water, or pure water? If tap water, look up your water utility's online water quality report. What is the value reported for total dissolved solids (TDS?) Much tap water includes sufficient calcium and magnesium for most plants. I suspect you aren't using tap water, or your tap water is low in calcium and magnesium.
There should be no problem using your fertilizer if you also give your plants magnesium and calcium. It takes quite a while (months) to replete magnesium stores, once depleted. Add a small amount of Epsom salts (1/4 teaspoon per gallon) to all your waterings. Or use a higher amount, less often.
People here report using plaster of Paris mixed into water to supplement calcium. If you use the Search function in the top maroon bar, and search on plaster, you can find these posts.
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