Hi, w8tah. Hazy yellow sounds like the start of green water (algae). The overdue gravel cleaning may have kicked up excess nutrients into the water - voila, algae explosion. The same thing happened to me awhile back.
Feed the fish and then do a 50% water change/gravel vac. Turn off the tank light and cover the tank completely with a heavy blanket - you want no light to get in. If you have an airstone, crank it up - or lower the water level somewhat so the filter splashes more to keep the water well oxygenated. Maintain the total blackout for 4 - 5 days - no feeding or peeking. After the blackout, do a 50% water change. The fish and most live plants will do fine without food or light for five days, but the algae will not! Good luck.