Each pig should have about a cup of veggies daily, preferably split up into 2 servings. The majority of the daily veg should be green or red leaf lettuce (Boston is good too) and include a veggie that is high in vitamin C; 1/8 of a bell pepper per pig daily should be enough to meet their vitamin C requirements. You also want to feed them somewhere between 5-10 veggies that are not leafy greens on a regular basis and only a small amount of fruit once every few weeks. If you'll look in the "nutrition" sub-forum, there should be a pinned topic with a chart of common fruits and vegetables and nutrition info on them. Your choice of vegetables may depend on what's in season, what's locally available/cost effective for you, and what your piggies like. Keep in mind that it's not necessary to feed all of your 5-10 veggie choices every day; as you'll find in the nutrition chart, some veggies should only be fed a limited number of times/amounts routinely. I used to rotate some combination of cherry tomatoes, baby carrots, cucumber, yellow squash, zucchini, and raddicchio throughout each day of the week.
Cucumber is a very good veggie to feed a few times per week. Keep in mind though that some pigs (but not all) may be sensitive to cucumber, especially in large amounts, and it can cause GI upset or bloating if they get too much at once. All new veggies should be introduced into the diet slowly, one veggie at a time, and increase the amount of that veg slowly until they are eating the amount you plan to routinely feed. Pigs have very delicate GI systems, and introducing a whole lot of a new food at one time or introducing multiple new foods at one time can cause GI upset. One last thing to keep in mind is that if you are seeing very large amounts of white deposit where their urine dries -- especially if the deposits feel "gritty" -- you might want to restrict the number/amount of veggies you feed that have a high calcium content (see the nutrition chart). Pretty much all pigs will produce some amount of white calcium deposits in their pee, but you don't want to be finding piles of it.
You are correct that tear-drop shaped poops are typically a sign of gut upset in one form or another. They commonly can be caused by the pig not eating enough when they are sick or by upset due to too many veggies or a new veggie that doesn't agree with them. The first thing you can try is to take away all veggies for 48 hours, and then start re-introducing veggies slowly -- one at a time and starting with lettuce -- all over again to see if there isn't one veggie that makes the tear-drop poops appear.
Monitor them both to make sure they are eating and drinking and pooping enough, don't seem lethargic, etc. Keep an eye on Oreo's sneezing and watch for any nasal discharge, runny eyes, weird breathing sounds or lethargy, as these would be signs of illness. Finally, make sure that you weigh your pigs weekly using a kitchen scale:
https://www.guinealynx.info/weigh.html This is one of THE MOST important ways to monitor their overall health and catch illness before it becomes dangerous.