My first thought is lighting; specifically, daylength. You probably know this already, but if the daylength dips below 10-11 hours its stops pitchering.

it is also possible that some fertilizer, perhaps too much, has accidentaly leaked into the soil, making it only grow pitcherless leaves, and lots of them.

Fertilizer "leaked into the soil" is a good thing. Pitcherless plants has nothing to do with fertilizer over dose or lack of. It could mean that other conditions in your environment is lacking (light, air circulation-too much not enough, media, and the worst case scenario, is that you own a tissue culture throw-back that won't make pitchers.
See my other posting regarding feeding nepenthes.
See image of a well fertilized regime showing nepenthes growing in as small as a four inch pots producing decent sized and colored pitchers. Lots of sun exposure and air circulation and of course watering.

Here is a link that might be useful: {{gwi:556241}}

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A plant cannot "over eat" if your plant is pitcher-less it is more likely a result that it is not receiving nutrients that it needs to 1.) stay alive, 2.) grow and develop and 3.) develop pitchers.
N. alata is a weedy species and there should be no excuse why it shouldn't be overcrowded with pitchers.
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All the time!

where do you buy your plants RainforestGuy? and do you know where plants can be bought that are seed grown and not tissue-cultured? I would prefer a unique plant, rather than a clone of someone elses plant. Don't get me wrong, tissue-culture is great for conservation and mass nursery sale, but that's about it.

Tissue culture is NOT great for conservation. Tissue culture is only great for nurseries who sell replicants of the same retards over and over again. Often just one clone, one sex and at best, nutated from what it started with.

Seed-grown plant material is good for conservation. When you have multiple seed-original seedlings circulating, why bother with wild collected plants when seed original well adapted species grows so much faster, better and with a good range of genetic gene pool variation that this alone will keep wild populations safe and sound.

Here is a batch of seed grown N. truncata
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Wild collected specimens are difficult to reestablish, death rates for smuggled collected plants are closer to 99%. Why does anyone want a wild nepenthes? Mostly because they have new gene pool/genetic material (only available in seed originals) and that there is a better chance of having both male and female plants in your progeny(not the way that current growers sell unknown numbered "random" grown tissue cultured clones where no data on sex or anything is available) thus this tc production only serves the growers to sell more and more unknowns of whether they have clone 1, clone 2, or clone 3.

Between you and me they are only selling ONE single clone because the more you buy, the more $$$ they make. I don't like this kind of monopoly and this makes me mad! Stop right now and express that you will ONLY buy seed originals. EVERYTHING in my collection are seed originals. I do not own any tissue cultured plants of any thing!

Seed original plants make better seed development than tc retards.
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Seeds germinate better and more seeds are produced at a time than on weak barely surviving tc plants NOT fertilized.

You grew all of your plants from seed? that's cool. I agree, I used to think seed grown wouldn't be great because the plants are different, but I realized if the species are all gonna change over time any ways, than a well established seed grown plant could beat a lab experiment any day.

No I didn't grow all of them from seeds myself. I just bought from growers who did grow seed originals. This way the plant grows better and have the kinds of variations found in nature.

Tissue culture plants are exact replicas of the same thing, we even base our expectations on what we see since they are 100% like xerox copies.Same pitcher color, same growth habit, and same sex (one sex).

From a batch of seed grown originals, man will always select the best growing, biggest, more colorful, etc. characteristics to make seeds from.
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In tissue culture you're stuck with the one. Since tc starts originate from an embryo, you really don't know what you got until it matures. Thus making thousands of this unknown to sell and hope for the best. Usually the result is a mediocre if even that plant that we're stuck with. Seed originals give you options to select for the best clones and make cuttings from them. Increasing chances for everyone to have the plant that is desirable.

Besides fertilizing THE ROOT ZONE, good light, ample watering and good air circulation is a must!
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Give them room and they will grow
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Even small tiny plants can get huge and gargantuan
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But you gotta feed them!
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