Sorry, I am using an old version (1.10.2), but I've seen this issue in other mods, 1.12 is similar in many ways, and I'm too lazy to update at the moment so... If it's absolutely required then let me know, I guess.

Using DrawHoveringText makes items drawn afterward appear darker, despite the use of push/pop matrices. Github for my mod is here: https://github.com/zane49er2/VMC but the relevant code is likely here:

// Page links/items
		for (int i = 0; i < bItems.size(); i++) {
			BookItem b = bItems.get(i);
			int Tx = (int) (b.x) + xScroll;
			int Ty = (int) (b.y) + yScroll;
			float selSpeed = 0.05f;

			// draw
			GlStateManager.pushMatrix();
			if (Tx >= left && Ty >= top && Tx <= left + GUIWidth - 36 * b.scale && (float) Ty <= top + GUIHeight - 36 * b.scale) {
				// selection detection
				if (mouseX > Tx && mouseY > Ty && mouseX < Tx + 36 * b.scale && mouseY < Ty + 36 * b.scale) {
					b.hovering = true;
					b.r += selSpeed * (b.rSel - b.r);
					b.g += selSpeed * (b.gSel - b.g);
					b.b += selSpeed * (b.bSel - b.b);
				} else {
					b.hovering = false;
					b.r += selSpeed * (b.rn - b.r);
					b.g += selSpeed * (b.gn - b.g);
					b.b += selSpeed * (b.bn - b.b);
				}

				this.mc.getTextureManager().bindTexture(texture);

				GlStateManager.enableBlend();
				GlStateManager.translate(Tx, Ty, 0);
				GlStateManager.color(b.r, b.g, b.b, 1.0F);
				float borderSize = 1f;
				switch (b.bgType) {
				case 0:
					borderSize = 2f;
					break;
				case 1:
					borderSize = 1.3f;
					break;
				case 2:
					borderSize = 1f;
					break;
				case 3:
					borderSize = 1.5f;
					break;
				}

				GlStateManager.scale(b.scale, b.scale, b.scale);
				this.drawTexturedModalRect(0, 0, 36 * b.bgType, GUIHeight, 36, 36);

				GlStateManager.disableLighting();
				GlStateManager.enableCull();

				GlStateManager.translate(36 / 2, 36 / 2, 0);
				GlStateManager.scale(borderSize, borderSize, borderSize);
				GlStateManager.translate(-16 / 2, -16 / 2, 0);

				this.itemRender.renderItemAndEffectIntoGUI(new ItemStack(b.item), 0, 0);
				GlStateManager.blendFunc(GlStateManager.SourceFactor.SRC_ALPHA, GlStateManager.DestFactor.ONE_MINUS_SRC_ALPHA);
				GlStateManager.disableLighting();

			} else {
				b.hovering = false;
				// explode		
				int Px = (int) (b.x) + pxScroll;
				int Py = (int) (b.y) + pyScroll;

				if (Px >= left && Py >= top && Px <= left + GUIWidth - 36 * b.scale && (float) Py <= top + GUIHeight - 36 * b.scale) {
					for (int j = 0; j < (random.nextInt(100) + 15) * b.scale; j++) {
						BookSymbol s = new BookSymbol();
						s.u = (random.nextInt(5) * 16) + 170;
						s.v = random.nextInt(3) * 16;
						s.xv = (xScroll - pxScroll) * 10 + random.nextInt(50) - 25;
						s.yv = (yScroll - pyScroll) * 10 + random.nextInt(50) - 25;

						s.x = Px + random.nextInt((int) (36 * b.scale));
						s.y = Py + random.nextInt((int) (36 * b.scale));

						s.r = b.r;
						s.g = b.g;
						s.b = b.b;
						s.age = 1;
						s.noFadeIn = true;
						particles.add(s);
					}
				}
			}
			GlStateManager.popMatrix();
			// tooltip
			if (b.hovering) {
				List<String> j = new ArrayList<String>();
				j.add(b.name);
				GlStateManager.pushMatrix();
				drawHoveringText(j, mouseX, mouseY, fontRendererObj);
				GlStateManager.popMatrix();
			}

			// update previous scroll
			this.pxScroll = xScroll;
			this.pyScroll = yScroll;

		}

 

I'm not certain, but I think the matrix only applies to transformations (like translations, scaling, rotations). I'm not sure that the blending, colors and lighting are part of the matrix.

 

I would try to save all the blending, color and lighting settings before you change them, then restore them at the end and see if that fixes is.

Wow, that was the entire problem. I moved the lighting, cull, and blendfunction lines to the top and now it works.