Oh, wow, 10 years ago! There is a special tool meant just for grout removal, your local hardware store should have it. It will be time consuming but aside from removing everything it's probably the way you'll need to go.

I agree with divadeva. More lights. If you can add pot lights do it. If they're already there add task lighting and up the wattage on the bulbs on the pot lights (replace with LED and you can make them brighter because the wattage on LED is lower for brighter light). If you have all of that add decorative lighting. If ventilation is an issue find a way to move the air around or add air filtration. Maybe the HVAC is deficient. Maybe you can add a HEPA filter instead of the standard one that comes with the unit. Call an HVAC specialist to see if there is a way to boost air flow in the room.

I did a house with nine bathrooms and it was so much fun. For the master bed we had his and hers separate ensuite bathrooms, so hers was feminine and victoruan; it even had a chandelier! His was white with a red shower wall and a blue and white border tile. The counter was tiled with red. It was a very cheerful little bathroom. The daughter's batH was blue and white, the border tiles and washbasin were Chinese themed. A very pretty bathroom. The two guest bathrooms were yellow and cream with hand painted sunflower accent tiles. One powder room was yellow and white, the other was beige with orange and green accents. It had a very whimsical washbasin with a hand painted frog inside. The pool house also has two bathrooms, more basic, mostly cream with wood accents. The colour comes from the stack of towels, red, blue, orange, lime green and yellow.

I have used both with good results. The main difference between Quartz and Granite are 1) price, 2) colour range. Granite generally works out cheaper, because you can buy the exact quantity you require. Quartz comes in large slabs of specific sizes- standard size being roughly 10'-0" x 4'6", so there tends to be more wastage if you don't plan the cutting well. But Quartz is pretty and comes in a wide range of colours and can be re-buffed at a later date. Quartz also comes in various thicknesses- the most commonly used being .75" to about 1.25". And especially when you use dark wood cabinets in a kitchen or bathroom, beige and white counter tops work very well. Some people go even with coloured counter tops like blue, orange, yellow. Natural stone in light colours tend to be porous and stain easily, so I prefer to go with pure black which is safe.