Sago Palm houseplant
I bought my Sago last fall, and it had six healthy leaves about 10" tall. The potting mix is loose, fine and has no perlite. Early this year, a leaf turned completely tan, and the greenhouse said that they will lose leaves normally. (???) So I adjusted my watering to light applications every week or so when the mix was dry over one inch deep. Over the months, two more leaves went tan, but the remaining green leaves stayed that way until about ten days ago. Now, about every day, a leaflet turns tan starting at the bottom, and it's up to eight leaflets now. My moisture meter shows very high top to bottom, but finger-sticking two inches down shows bone dry. One website says it may be a magnesium deficiency. I'd go back to that site to confirm, but I suspect this answer would be deleted. I water from the top, but not in the "pineapple-like" protrusion sticking out of the soil. Sago overwatering seems to be a common theme in books as a particular problem. Help. Thank you. Sago and caretaker.
Without actually seeing your plant, it is not always possible to diagnose a problem. But from your description, it really sounds like underwatering. The bottom line is if you stick your finger in the soil and it feels dry, it is. I find both those moisture and pH meters to vary considerably in their accuracy.
Maybe you can lift the plant out of the pot and then you can really tell the condition of the roots. The soil should be moderately moist and the roots should be white. You should water enough so that a bit of water runs out the bottom but not allow the plant to sit in a saucer full of water.
As far as nutrient deficiencies go, if you are fertilizing with a complete houseplant fertilizer with micronutrients and calcium and magnesium, your plant should be getting all the nutrients it needs. Even if it was deficient in a nutrient, with the leaves turning brown at the rate you are seeing, it would probably not matter if nutrients were added now.
So I would really remove the plant from the pot and look at the moisture level in the pot and for the amount of healthy white roots and use the results to adjust your watering levels. If by some chance the root zone has completely dried out, there is a good chance that the plant will not make a come back.
You did not mention what temperature you keep the plant at. If it is on the warm side, you would have to water more often and vice verse if kept on the cold side.