Hi! There's a Sansevieria forum on here. You may want to ask there. It looks like something has been chewing on your plant, or something was splashed on it. I wouldn't wait to find out what the problem is, or was, to remove that leaf as close to the soil surface as possible. Do any other leaves look like that?

Chris, it is obvious to me, from your photos, and the size of the leaf that this is an older leaf. Because of the size. Your newest leaves are much taller, right? Sans are a group unto themselves. I've been met with much resistance on this form (years ago, I've been 'away') about the sans tip spike. Your plants are beautifully healthy and you have nothing to worry about. Plants have a finite life, somewhere between puppies and fish. So, older leaves fail first. It is a circle-of-life thing and easily explained when looking at a plant that is more than a few months old. Hoyas have leaves that fail around the same time leaving you with a plant full of yellowing, failing leaves... leading to freak out and 'WHAT did I DO?!' Nothing, they just all grew around the same time, hit old age around the same time, and left you in that plant parent place. Because everything else about this plant looks spectacular, I think this is just an 'age' thing. The white spots on the leaf can be a wax thing, or a water spot 'calcium' deposit best solved with a vinegar wash. White or cider vinegar, on a cotton ball or paper towel tested on an out-of-the-way spot. I've used vinegar on all from orchids to crotons... Softer leaved plants do NOT benefit. T'will make your babies look like they JUST stepped out of the salon. Now, my controvertial statement about tip spikes is this: Once the spike is broken, the leaf stops growing. If you allow the spikes protection and space, you can specifically control size by snapping the spike where you want the leaf to stop. (Yes, I have photographic evidence, but this post is about your plant, your issues.) Your plant looks wonderful to me. Listen to Toni, she is an HP expert! I ALWAYS ask her citrus questions!

Looks like chlorosis. There are many reasons this could happen. Aglaonema needs a lot of light and a lot of heat. It needs at least 70 degrees, 75 is better. It's soil should never get below 65-68, bottom heat may be needed also. It could also be a deficiency. Try giving them a little epsom's salt, about 1/2 tablespoon to a gallon of warm water to dissolve it. Let it get to room temp and water both of them. Move them to a south facing window, you may need to supplement the light and heat. I would also check for spider mites. Put a white piece of paper under a leaf and flik it. If they are mites, there will be microscopic black dots on the paper.

Your soil looks fine in that photo.......lots of perlite and can't really overwater it. When you water try not to wet the actual crown/leaves of the plant (just the soil/roots), and water on the morning of a bright day. These are both more applicable in winter. Your biggest problem growing that plant was lack of light. Unfortunately those etiolated/stretched leaves will not heal or turn normal. Assuming the crown is healthy, and growing conditions remain good, it will eventually produce another normal pup or two. Keep it under good growing conditions. You may just want to buy a new plant and grow in the better conditions you are providing now.