If you search for pictures of nitrogen burn on the plants you grew last year you can see if that visually matches what you saw: you said the plants appeared to "die from the ground up?"
If you didn't use a lot of chicken poo and it was aged for three months I'm guessing it's unlikely that you burned your plants doing that. But I could be wrong
There's nothing magical about chicken poo. It's just very high in nitrogen. That's what the white stuff on the poo is: urea. Mammals excrete urea in urine (hence the name), but birds excrete it with their solid waste. So if you're using mammal poop as fertilizer, by definition, it is much lower in nitrogen than any poultry manure. So you won't risk burning your plants with it.
Nitrogen is the most volatile of the plant nutrients. It readily leaches into the ground as nitrates when it gets rained into the soil. But too much rain and it travels right past the root zone and into the groundwater where it becomes a pollutant. Or if it sits wet on the surface of the ground and isn't consumed by plants or other composting organisms (like the kind that break down woody proteins) then it will be released into the atmosphere as ammonia. If you can smell ammonia in your compost pile, add some carbon material. That way the N won't get wasted
Both are likely to happen to some degree or another as you age a manure pile. That's why you won't burn plants nearly as easily with aged chicken poop.
But it's also a shame to be losing those nutrients that could be put to very good use in your garden!
That is part of the heart of composting. The longer compost ages, the more humus will result, but the fewer nutrients it will contain. Fully composted material has very little nutritional value for plants. But it's almost 100% invaluable, soil-building humus. Less composted material has more nutrients for plants, but isn't broken down into humus. You need bio-available (aka mineralized) plant nutrients AND organic matter (humus) for plants (and everything else in the soil) to really thrive.
Don't be afraid to experiment to find out how your chicken poo piles and garden will play together optimally. Perhaps try different methods in different areas each season? If you had a little patch that you wanted to grow nitrogen-loving veggies on, perhaps try incorporating a generous amount of fresh chicken poo in part of that patch of soil four weeks before (trans)planting. What are the differences in the plants between the poo and non-poo treated areas?
For things you DON'T want lots of unnecessary vegetative growth out of (e.g. tomatoes) DON'T incorporate fresh(ish) chicken poo at all. Use aged stuff or try mammalian poo.
Also note that phosphorus and especially potassium do NOT readily leach out of soil. If you add a lot of animal manure to the same patch of soil year after year you can build up too much of both P and K and that will create it's own set of problems.
I like to think of forests and grasslands. How much animal poop is required to keep those wild lands fertile? Essentially none. The plants (and the organisms living with the plants) do almost all of their own nutrient recycling. The poop is incidental.
I'm trying to garden the same way
Green manures for the win! My long term goal is no fertilizers whatsoever. Ask me in the fall how well my first season trying this went
