In our case, we have a quart of solid yeast, with the added wort it will be 1/2 gallon total slurry. This is used for 10 gallon batch sizes.
If you are pitching a quart of thick yeast slurry into 10-gallons of wort, you are way overpitching. That is why your crops are pooping out on you. The suggested pitching rate for one barrel of wort is 1L of slurry. That rate breaks down to approximately 33ml per gallon, or 330ml for 10 gallons. The pitching rate for 5 gallons is 5 * 33ml = 165ml of thick slurry. Overpitching results in reduced new cell production, which over the long haul results in loss of culture viability. It is always better to underpitch than overpitch when serially re-pitching a culture. A milliliter of thick slurry contains between 1 and 2 billion cells. The standard practice value is 1.2 billion cells per milliliter. One liter of thick slurry contains 1.2 trillion cells. Maximum cell density for 10 gallons is 38 * 200B = 7.6 trillion cells. If we start out with 1.2 trillion cells we only get log2(7.6 / 1.2) = log(7.6 / 1.2) / log(2) = 2.66 replication periods before maximum cell density is reached. The average batch when pitched correctly goes through 4 to 5 replication periods, which means that the new cell to old cell ratio in the culture is higher than the way you are pitching. Overpitching may result in a faster onset of active fermentation, but it comes at the cost of new cell growth, which over time degrades the quality of the culture.