Question
With proper watering and plant food, what is causing the end of some of the leaves to turn yellow and brown? The plant gets plenty of indirect sunlight.

Thank you for any help you might be able to share.

Answer
William,
Depends on what you consider proper watering and fertilizing.
Water your plants in the following manner. I water most of my plants this way. Check how much the plant weighs when thoroughly watered VS its' weight when it is ready to be watered again. Sometimes it helps to put a saucer under the pot and let the plant sit in water for 10-15 minutes. After that pour off the excess water. Pick the pot up ( or lean it if it a large pot ) and feel how heavy it is after watering it thoroughly. Don't water it again until it feels considerably lighter and the top of the soil is light in color. Mother Nature doesn't water once a week/ month/ etc. ...Depending on plant types, sunlight exposure and pot size plants will need water at many different rates from once a day to once a month or more. You should turn the plant a 1/4 turn once per week to keep the growth even. Plants do need to be fertilized every month or so during their active growing period to stay healthy...
They do not like direct sunlight unless it is morning sun...Peace lilies will show signs of wilting if you let them go too dry between waterings...Spray misting the foliage 1-2 times per week will help stop yellowing and drying of the leaves...  
Remove yellow leaves when they become unsightly...
Hope this helps.  
Rick in Southern NJ