My triplets are almost the exact same age as Joey's. We are 6.5 months actual (5 adj) and I SWEAR this is a stage thing.
I used to stress about feeding time and almost dread it in a way. I loved the person that talked about the amount being min vs temper being high because it is SO TRUE. I would get so frustrated and I'm sure the babies could pick up on that. Next thing you know we would hit a growth spurt and be out of it only to return a few weeks later. It seems like for us 6 months has been a much better "stage". I don't know if it was a combination of things, age, etc but here's what we did.
First we have been off high calorie formula since 4 months. We use Earth's Best and this was after trying a few different ones and the girls love it. We also went from a three hour schedule during the day to a four hour and slowly increased the volume over time to compensate for the oz. We are also on solids and that has helped. All of these things seemed to really work for our girls and we have seen so many vast improvements I can hardly believe it. Our schedule is very similar to a PP's:
7am- Bottle
7:30a-8:30a- Nap
9-9:30am- Solids
11am- Bottle
11:30-12- Nap
12-12:30p- Solids
3pm- Bottle
3:30p-5p- Nap
5:30-6p- Solids (if hungry)
7pm- Bottle
I know we have more solids in than most at this age but our girls started taking full 8.5oz bottles at each of their feeds and wanted more. They are still taking 33oz a day plus all that solids.. If you had told me this would be happening a few months ago I would have laughed.
Also the scale is a curse. I am JUST like you and would weigh the girls at every bath and sometimes in between, I have finally asked my husband to take the scale away because we are on the charts and eating well. I think it's a NICU thing about weight and feedings and a really hard habit to break. I look at it as De-Nicutizing. Weight wise we used to pack on the oz and now seemed to have slowed down quite a bit even though they get A LOT of food. I've really worked hard and have stopped stressing about it and it's SO much better. As long as they are happy, healthy and gaining weight then I'm happy. I think this is a age stage thing as well between 6 and 9 months like someone said. They are so much more active right now it has to be hard to not keep burning the calories off.
As much as it sucks I would just grin and bear it until this stage wears off and I bet that it eventually will. Set a time limit for yourself so you are not sitting there for an hour fighting them. Let one just chill while you feed one or two of the others. I read somewhere that you can throw off their internal full switch by forcing them to eat when they don't want to. I feel your pain and hope things get better REALLY soon!

Erin

http://identicaltripletgirls.blogspot.com/

Erin
http://identicaltripletgirls.blogspot.com/

Avery, Morgan and Tatum
33 Weeks: 3lbs 8oz, 3lbs 11oz, 3lb 13oz