How often are you watering. Mine don't mind drying out a fair bit between waterings. They're also supposed to quite tolerant of lower light levels. Full sun is very bad though.

Where did the leaves begin to brown. Was it the tips? Could've just been dry air.

I think maybe just give it some shade, and make sure you're not overwatering.

I agree with Bunny. Mine all grow well for years in a shaded north/northeast window with little to no direct sun at all. They are all 2 to 3 feet in diameter with babies and in 10 to 12 inch plastic pots of one part bagged african violet soil and 1 part perlite (the soil is very light) and are watered when it is fairly dry, about once every 7 to 10 days in my conditions of 50 to 60+ percent humidity. No experience at all with coconut fiber lining for houseplants, the ones I've seen available are too big for mine. What type of soil are you using? Heavy soil may be keeping the plant wet for too long and if the pot is also too big the roots could be drowning. I keep the pots about 2 inches larger than the root system. Extra soil here tends to keep the plants wet too long so the leaves will brown and die back.

I put it in Miracle Grow potting soil mix with moisture control.

Some info from something I posted previously:

While necrotic leaf tips or margins can occur in this plant from over/under-watering, in fact, it's much more common for the actual cause to be a high level of soluble salts in soils. It's also commonly reported that this plant is particularly intolerant or fluoride, but it's still more common for the cause of leaf burn to be a high level of solubles, to which fluoride can be a contributor, than it is to be fluoride itself. WHEN there is a high level of salts in the soil, low humidity can be a contributor, but low humidity alone rarely presents an issue, it must be in combination with a high level of soluble salts in the soil or either over/under-watering.

Of course, you cannot correct the already burned tips (they won't 'heal'), but you can take steps to keep it from happening:

A) Most important is to use a soil that drains very freely. This allows you to water copiously, flushing the accumulating salts from the soil each time you water.

B) Fertilize frequently when the plant is growing well, but at low doses - perhaps 1/4 the recommended strength. This, in combination with the favorable watering habit described above, will keep soluble salts levels low, and keep levels from rising due to the accumulative effect we always see when we are forced to water in sips when plants are in water-retentive soils.

C) When watering, using rainwater, snow melt, water from your dehumidifiers, or distilled water also eliminates the soluble salts in your tap water and will go a long way toward eliminating or minimizing leaf burn.

D) If you make your own soils and use perlite, be sure the perlite is rinsed thoroughly, which removes most of the fluorides associated with it's use.

E) Allowing water to rest overnight doesn't do anything in the way of helping reduce the amount of fluoride (the compounds are not volatile), and it only helps with chlorine in certain cases, depending on what method of chlorination was used to treat your tap water.

Al