Ok first, please don't take this the wrong way I'm not being snarky or snide I'm just explaining.
If your not using the tpg supplement you aren't feeding tpg correctly and the gliders may not be getting what they need from the diet your feeding.
Tpg's supplements are designed to provide essential vitamins and minerals that their diet specifically needs to be balanced. Other brands ingredients are not calculated with the rest of the diet, tpg supplements are.
So I would suggest either using the tpg supplement or change diets to one that doesn't require supplements being sprinkled on such as bml, or critter love.
If the gliders dietary needs aren't being met that is a good reason for food aggression to start. It may seem sudden but it's probably not. What I mean is, what ever they are lacking from their food was at ok levels before, over time those levels have dropped in their body and aren't being replenished.
not following a specific diet correctly is not uncommon. Diets can be very confusing and there are a lot of modified versions online that shouldn't be used but are anyway. Any diet whether it's bml, tpg, critter love etc... should be followed to the letter of the creator of that diets directions.
The ingredients and measurements are there for a reason, once either of those are modified it's no longer the same diet or balanced.